Remove a third DiagnosticBuilder::emit_without_consuming call.

It's not clear why this was here, because the created error is returned
as a normal error anyway.

Nor is it clear why removing the call works. The change doesn't affect
any tests; `tests/ui/parser/issues/issue-102182-impl-trait-recover.rs`
looks like the only test that could have been affected.

compiler/rustc_parse/src/parser/generics.rs

@@ -77,7 +77,6 @@ impl<'a> Parser<'a> {
                                     Applicability::MachineApplicable,
                                 );
                             }
-                            err.emit_without_consuming();
                             return Err(err);
                         }
                     }