'main': Update $this_word state with our inferences.

Found by code inspection.

highlighters/main/main-highlighter.zsh

@@ -592,6 +592,7 @@ _zsh_highlight_main_highlighter_highlight_list()
           # Not an option flag; nothing to do.  (If the command line is
           # syntactically valid, ${this_word//:sudo_opt:/} should be
           # non-empty now.)
+          this_word=${this_word//:sudo_opt:/}
         fi
       elif [[ $this_word == *':sudo_arg:'* ]]; then
         next_word+=':sudo_opt:'