Don't emit empty notes

src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr

@@ -8,8 +8,6 @@ LL |     let Ok(x) = res;
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
 note: `Result<u32, &R<'_>>` defined here
   --> $SRC_DIR/core/src/result.rs:LL:COL
-   |
-   = note: 
 $SRC_DIR/core/src/result.rs:LL:COL: not covered
    = note: the matched value is of type `Result<u32, &R<'_>>`
 help: you might want to use `if let` to ignore the variant that isn't matched