Fix regex

Author: josevalim

lib/elixir/test/elixir/kernel/expansion_test.exs

@@ -2551,7 +2551,8 @@ defmodule Kernel.ExpansionTest do
         expand(code)
       end
 
-      message = ~r["a -1..a+1" looks like a function call but there is a variable named "a"]
+      message =
+        ~r["a -1\.\.\(a \+ 1\)" looks like a function call but there is a variable named "a"]
 
       assert_raise CompileError, message, fn ->
         code =