Delete `tests/crashes/23707.rs` because it's flaky
It's conditioned on `only-x86_64` because it doesn't reliably fail on other platforms, it's optimization dependent and failed to ICE post-PGO in
<https://github.com/rust-lang/rust/pull/132300#issuecomment-2443279042>. Remove this test for now without prejudice against relanding the test in a more reliable form.
I removed the `S-bug-has-test` label from #23707.
r? compiler