Delete tests/codegen/fmt_int_no_panic.rs

this test was included for demonstrative and discussion purposes but does not test what its name alleges - in fact it does not test much of value at all!

as mentioned in this comment, https://github.com/rust-lang/rust/pull/122770#issuecomment-2474256965 , writing a correct test for this codegen outcome is difficult (partially because the public interface to std::fmt intentionally includes an #[inline(never)] function!), so to test this correctly will require more than i can offer in 122770.

tests/codegen/fmt_int_no_panic.rs

@@ -1,24 +0,0 @@
-// Trying to check that formatting u8/u32/u64/etc do not panic.
-//
-// This test does not correctly do so yet.
-
-//@ compile-flags: -O
-
-#![crate_type = "lib"]
-
-// expected to need to write some kind of `impl core::fmt::Write` on a struct like this to avoid
-// unrelated panics if `String::write_str` can't make space..
-// struct CanAlwaysBeWrittenTo;
-
-use std::fmt::Write;
-
-// CHECK-LABEL: @format_int_doesnt_panic
-#[no_mangle]
-pub fn format_int_doesnt_panic(s: &mut String) -> std::fmt::Result {
-    // CHECK-NOT: panic
-    // ... but wait! this will definitely panic if `s.vec.reserve_for_push()` cannot alloc! this
-    // shouldn't pass!
-    write!(s, "{:x}", 0u8)?;
-    write!(s, "{:x}", u8::MAX)?;
-    Ok(())
-}