yecc instead of yeec (#4813)

Typo. should be `yecc` instead of `yeec` in the documentation

Signed-off-by: José Valim <[email protected]>

Author: wende

lib/mix/lib/mix/tasks/compile.ex

@@ -11,7 +11,7 @@ defmodule Mix.Tasks.Compile do
   ## Configuration
 
     * `:compilers` - compilers to run, defaults to:
-      `[:yeec, :leex, :erlang, :elixir, :xref, :app]`
+      `[:yecc, :leex, :erlang, :elixir, :xref, :app]`
 
     * `:consolidate_protocols` - when `true`, runs protocol
       consolidation via the `compile.protocols` task