Remove useless subkind infer

Co. #1971

> For the sigil part, I checked https://docs.perl6.org/js/search.js and lookup https://docs.perl6.org/language/variables.html#index-entry-%21%2525_%28sigil%29

> All sigil are X<>-ed manually. I'd like to remove 'sigil' from the very line, since its meaning is weird. If we want to make something searchable/indexed, use X<> as Pod6 spec.

Author: tisonkun

htmlify.p6

@@ -593,7 +593,7 @@ sub find-definitions(:$pod, :$origin, :$min-level = -1, :$url) {
                             :$summary,
                     ;
                 }
-                when 'variable'|'sigil'|'twigil'|'declarator'|'quote' {
+                when 'variable'|'twigil'|'declarator'|'quote' {
                     # TODO: More types of syntactic features
                     %attr = :kind<syntax>,
                             :categories($subkinds),