Remove the redundant span_label.

src/libsyntax/parse/parser.rs

@@ -3158,7 +3158,6 @@ impl<'a> Parser<'a> {
             let in_span = self.prev_span.between(self.span);
             let mut err = self.sess.span_diagnostic
                 .struct_span_err(in_span, "missing `in` in `for` loop");
-            err.span_label(in_span, "expected `in` here");
             err.span_suggestion_short(in_span, "try adding `in` here", " in ".into());
             err.emit();
         }

src/test/ui/issue-40782.stderr

@@ -2,10 +2,7 @@ error: missing `in` in `for` loop
   --> $DIR/issue-40782.rs:12:10
    |
 12 |     for i 0..2 {
-   |          ^
-   |          |
-   |          expected `in` here
-   |          help: try adding `in` here
+   |          ^ help: try adding `in` here
 
 error: aborting due to previous error