'main': Apply the parameter expansion logic regardless of the type

The existing check was bogus: parameter expansion doesn't depend on
whether there happens to be a command literally called «$foo».

This enables the parameter elision logic to kick in for words not in
command position.

Fixes #239.

highlighters/main/test-data/order-path-after-dollar.zsh

@@ -28,6 +28,7 @@
 # vim: ft=zsh sw=2 ts=2 et
 # -------------------------------------------------------------------------------------------------
 
+local foo='is set'
 touch '$foo'
 BUFFER=': $foo \$foo'