tests: Remove invalid target_env cfg

[polarathene]

When looking at the CI test logs, there is this warning emitted:

warning: unexpected `cfg` condition value: `gnueabi`
  --> tests/example_crates.rs:26:11
   |
26 |     #[cfg(target_env = "gnueabi")]
   |           ^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: expected values for `target_env` are: ``, `gnu`, `macabi`, `mlibc`, `msvc`, `musl`, `newlib`, `nto70`, `nto71`, `nto71_iosock`, `nto80`, `ohos`, `p1`, `p2`, `p3`, `relibc`, `sgx`, `sim`, `uclibc`, and `v5`
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
   = note: `#[warn(unexpected_cfgs)]` on by default

Associated section:

c-ward/tests/example_crates.rs

Lines 26 to 31 in f71902a

	#[cfg(target_env = "gnueabi")]
	let env = "gnueabi";
	#[cfg(all(target_env = "gnu", target_abi = "eabi"))]
	let env = "gnueabi";
	#[cfg(all(target_env = "gnu", not(target_abi = "eabi")))]
	let env = "gnu";

These were added in Sep 2023 and accompanied with a feature gate #![feature(cfg_target_abi)] (which stabilized in Rust 1.78.0 in May 2024, related discussion) that was dropped in from tests/example_crates.rs in March 2024 as part of the nightly version bump.

[sunfishcode]

Thanks!