Remove a third DiagnosticBuilder::emit_without_consuming call.

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

Author: nnethercote

compiler/rustc_parse/src/parser/generics.rs

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