Rollup merge of #101556 - compiler-errors:tweak-generator-print, r=jackh726

Tweak future opaque ty pretty printing

1. The `Return` type of a generator doesn't need to be a lang item just for diagnostic printing of types
2. We shouldn't suppress the `Output = Ty` of a opaque future if the type is a int or float var.

compiler/rustc_span/src/symbol.rs

@@ -763,7 +763,6 @@ symbols! {
         gen_future,
         gen_kill,
         generator,
-        generator_return,
         generator_state,
         generators,
         generic_arg_infer,