build: untrack _build/ and deps/ (already in .gitignore)

Build artifacts and downloaded deps were committed before .gitignore
existed and have stayed tracked since. Any recompile (like yesterdays
dispatcher fix landing) dirties them and the next morning auto-repair
commits the BEAM diff as if it were work. git rm -r --cached makes
the existing .gitignore actually do its job.

_build/dev/lib/bandit/ebin/bandit.app

@@ -1 +0,0 @@
-{application,bandit,[{modules,['Elixir.Bandit','Elixir.Bandit.Adapter','Elixir.Bandit.Application','Elixir.Bandit.Clock','Elixir.Bandit.Compression','Elixir.Bandit.DelegatingHandler','Elixir.Bandit.Extractor','Elixir.Bandit.HTTP1.Handler','Elixir.Bandit.HTTP1.Socket','Elixir.Bandit.HTTP2.Connection','Elixir.Bandit.HTTP2.Errors','Elixir.Bandit.HTTP2.Errors.ConnectionError','Elixir.Bandit.HTTP2.Errors.StreamError','Elixir.Bandit.HTTP2.FlowControl','Elixir.Bandit.HTTP2.Frame','Elixir.Bandit.HTTP2.Frame.Continuation','Elixir.Bandit.HTTP2.Frame.Data','Elixir.Bandit.HTTP2.Frame.Flags','Elixir.Bandit.HTTP2.Frame.Goaway','Elixir.Bandit.HTTP2.Frame.Headers','Elixir.Bandit.HTTP2.Frame.Ping','Elixir.Bandit.HTTP2.Frame.Priority','Elixir.Bandit.HTTP2.Frame.PushPromise','Elixir.Bandit.HTTP2.Frame.RstStream','Elixir.Bandit.HTTP2.Frame.Serializable','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.Continuation','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.Data','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.Goaway','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.Headers','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.Ping','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.Priority','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.RstStream','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.Settings','Elixir.Bandit.HTTP2.Frame.Serializable.Bandit.HTTP2.Frame.WindowUpdate','Elixir.Bandit.HTTP2.Frame.Settings','Elixir.Bandit.HTTP2.Frame.Unknown','Elixir.Bandit.HTTP2.Frame.WindowUpdate','Elixir.Bandit.HTTP2.Handler','Elixir.Bandit.HTTP2.Settings','Elixir.Bandit.HTTP2.Stream','Elixir.Bandit.HTTP2.StreamCollection','Elixir.Bandit.HTTP2.StreamProcess','Elixir.Bandit.HTTPError','Elixir.Bandit.HTTPTransport','Elixir.Bandit.HTTPTransport.Bandit.HTTP1.Socket','Elixir.Bandit.HTTPTransport.Bandit.HTTP2.Stream','Elixir.Bandit.Headers','Elixir.Bandit.InitialHandler','Elixir.Bandit.Logger','Elixir.Bandit.PhoenixAdapter','Elixir.Bandit.Pipeline','Elixir.Bandit.PrimitiveOps.WebSocket','Elixir.Bandit.SocketHelpers','Elixir.Bandit.Telemetry','Elixir.Bandit.Trace','Elixir.Bandit.TransportError','Elixir.Bandit.WebSocket.Connection','Elixir.Bandit.WebSocket.Frame','Elixir.Bandit.WebSocket.Frame.Binary','Elixir.Bandit.WebSocket.Frame.ConnectionClose','Elixir.Bandit.WebSocket.Frame.Continuation','Elixir.Bandit.WebSocket.Frame.Ping','Elixir.Bandit.WebSocket.Frame.Pong','Elixir.Bandit.WebSocket.Frame.Serializable','Elixir.Bandit.WebSocket.Frame.Serializable.Bandit.WebSocket.Frame.Binary','Elixir.Bandit.WebSocket.Frame.Serializable.Bandit.WebSocket.Frame.ConnectionClose','Elixir.Bandit.WebSocket.Frame.Serializable.Bandit.WebSocket.Frame.Continuation','Elixir.Bandit.WebSocket.Frame.Serializable.Bandit.WebSocket.Frame.Ping','Elixir.Bandit.WebSocket.Frame.Serializable.Bandit.WebSocket.Frame.Pong','Elixir.Bandit.WebSocket.Frame.Serializable.Bandit.WebSocket.Frame.Text','Elixir.Bandit.WebSocket.Frame.Text','Elixir.Bandit.WebSocket.Handler','Elixir.Bandit.WebSocket.Handshake','Elixir.Bandit.WebSocket.PerMessageDeflate','Elixir.Bandit.WebSocket.Socket','Elixir.Bandit.WebSocket.Socket.ThousandIsland.Socket','Elixir.Bandit.WebSocket.UpgradeValidation']},{optional_applications,[]},{applications,[kernel,stdlib,elixir,logger,thousand_island,plug,websock,hpax,telemetry]},{description,"A pure-Elixir HTTP server built for Plug & WebSock apps"},{registered,[]},{vsn,"1.10.3"},{mod,{'Elixir.Bandit.Application',[]}}]}.

_build/dev/lib/hpax/ebin/hpax.app

@@ -1 +0,0 @@
-{application,hpax,[{modules,['Elixir.HPAX','Elixir.HPAX.Huffman','Elixir.HPAX.Table','Elixir.HPAX.Types']},{optional_applications,[]},{applications,[kernel,stdlib,elixir]},{description,"Implementation of the HPACK protocol (RFC 7541) for Elixir"},{registered,[]},{vsn,"1.0.3"}]}.