Fix invalid clippy suggestion

Author: estebank

src/tools/clippy/clippy_lints/src/unnecessary_wraps.rs

@@ -144,7 +144,7 @@ impl<'tcx> LateLintPass<'tcx> for UnnecessaryWraps {
                 (
                     "this function's return value is unnecessary".to_string(),
                     "remove the return type...".to_string(),
-                    snippet(cx, fn_decl.output.span(), "..").to_string(),
+                    "()".to_string(),
                     "...and then remove returned values",
                 )
             } else {

src/tools/clippy/tests/ui/unnecessary_wraps.stderr

@@ -126,6 +126,8 @@ LL | | }
    |
 help: remove the return type...
    |
+LL - fn issue_6640_1(a: bool, b: bool) -> Option<()> {
+LL + fn issue_6640_1(a: bool, b: bool) -> () {
    |
 help: ...and then remove returned values
    |
@@ -152,6 +154,8 @@ LL | | }
    |
 help: remove the return type...
    |
+LL - fn issue_6640_2(a: bool, b: bool) -> Result<(), i32> {
+LL + fn issue_6640_2(a: bool, b: bool) -> () {
    |
 help: ...and then remove returned values
    |