Revert "Fix highlight for atoms containing @ character"

This reverts commit eb06df6.

Author: jbodah

spec/syntax/atom_spec.rb

@@ -88,19 +88,4 @@ def project do
     end
     EOF
   end
-
-  it 'detects atoms containing @ in it' do
-    expect(<<~EOF).to include_elixir_syntax('elixirAtom', '@somewhere')
-      :atom@somewhere
-    EOF
-    expect(<<~EOF).to include_elixir_syntax('elixirAtom', '@somewhere')
-      [atom@somewhere: nil]
-    EOF
-  end
-
-  it 'detects atoms containing Unicode letters in it' do
-    expect(<<~EOF).to include_elixir_syntax('elixirAtom', 'ó')
-      :atóm
-    EOF
-  end
 end

syntax/elixir.vim

@@ -41,9 +41,9 @@ syn match   elixirOperator '\\\\\|::\|\*\|/\|\~\~\~\|@'
 
 syn match   elixirAlias '\([a-z]\)\@<![A-Z]\w*\%(\.[A-Z]\w*\)*'
 
-syn match   elixirAtom '\(:\)\@<!:\%([a-zA-Z_]\%(\w\|@\|\P\)*\%([?!]\|=[>=]\@!\)\?\|<>\|===\?\|>=\?\|<=\?\)'
+syn match   elixirAtom '\(:\)\@<!:\%([a-zA-Z_]\w*\%([?!]\|=[>=]\@!\)\?\|<>\|===\?\|>=\?\|<=\?\)'
 syn match   elixirAtom '\(:\)\@<!:\%(<=>\|&&\?\|%\(()\|\[\]\|{}\)\|++\?\|--\?\|||\?\|!\|//\|[%&`/|]\)'
-syn match   elixirAtom "\%([a-zA-Z_]\%(\w\|@\|\P\)*[?!]\?\):\(:\)\@!"
+syn match   elixirAtom "\%([a-zA-Z_]\w*[?!]\?\):\(:\)\@!"
 
 syn keyword elixirBoolean true false nil