Rollup merge of #110203 - compiler-errors:rtn-dots, r=eholk

Remove `..` from return type notation

`@nikomatsakis` and I decided that using `..` in the return-type notation syntax is probably overkill.

r? `@eholk` since you reviewed the last one

Since this is piggybacking now totally off of a pre-existing syntax (parenthesized generics), let me know if you need any explanation of the logic here, since it's a bit more complicated now.

compiler/rustc_resolve/src/late.rs

@@ -1116,7 +1116,6 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
                         }
                     }
                 }
-                GenericArgs::ReturnTypeNotation(_span) => {}
             }
         }
     }

compiler/rustc_resolve/src/lib.rs

@@ -312,7 +312,6 @@ impl<'a> From<&'a ast::PathSegment> for Segment {
                     (args.span, found_lifetimes)
                 }
                 GenericArgs::Parenthesized(args) => (args.span, true),
-                GenericArgs::ReturnTypeNotation(span) => (*span, false),
             }
         } else {
             (DUMMY_SP, false)