Update regression test for rust-lang#87481

This has been causing failures in CI here and
in rust-lang#90408. A comment there
(rust-lang#90408 (comment))
suggested blessing the output; this commit does that manually.

Author: pierwill

src/test/ui/panics/panic-short-backtrace-windows-x86_64.run.stderr

@@ -5,5 +5,4 @@ stack backtrace:
    2: c
    3: b
    4: a
-   5: some Rust fn
 note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.