tests: parameter-to-global-alias.zsh: Do not use 'x' as dummy command

E.g. on Cygwin, 'x' is an external command, causing the test suite to fail:

  ## parameter-to-global-alias
  # BUFFER=$'$s'
  not ok 1 - [1,2] «$s» - expected (1 2 "unknown-token"), observed (1 2 "command").

Author: m0vie

highlighters/main/test-data/parameter-to-global-alias.zsh

@@ -28,8 +28,8 @@
 # vim: ft=zsh sw=2 ts=2 et
 # -------------------------------------------------------------------------------------------------
 
-alias -g x=y
-local s=x
+alias -g global_alias_which_hopefully_does_not_clash_with_an_external_command_name=y
+local s=global_alias_which_hopefully_does_not_clash_with_an_external_command_name
 
 BUFFER=$'$s'