Ignore compiler-messages test on beta
Rust beta has more detailed error messages than stable, making the test fail.
// This test fails for older compiler versions since the error messages are different.
#[rustversion::attr(before(1.43), ignore)]
#[cfg_attr(tarpaulin, ignore)]
-// The error messages are more detailed on nightly, thus breaking the test.
+// The error messages are different on beta and nightly, thus breaking the test.
+#[rustversion::attr(beta, ignore)]
#[rustversion::attr(nightly, ignore)]
#[test]
fn compile_test() {
