tests: Remove deprecated coverage-helper tests #2873

Job	Run time
test-llvm (14)	1m 52s
test (stable)	1m 54s
test-llvm (15)	1m 44s
test (beta)	1m 57s
test-llvm (16)	1m 43s
test (nightly)	2m 38s
test-llvm (17)	1m 55s
test (nightly, macos-latest)	2m 21s
test-llvm (18)	59s
test (nightly, windows-latest)	5m 1s
test-llvm (19)	1m 12s
deny / deny	15s
miri / miri	2m 15s
msrv / msrv	5m 47s
release-dry-run / prepare	5s
tidy / tidy	1m 13s
release-dry-run / build (aarch64-unknown-linux-gnu)	1m 53s
release-dry-run / build (aarch64-unknown-linux-musl)	1m 30s
release-dry-run / build (aarch64-apple-darwin, macos-13)	2m 39s
release-dry-run / build (x86_64-unknown-linux-gnu)	1m 4s
release-dry-run / build (x86_64-unknown-linux-musl)	1m 13s
release-dry-run / build (x86_64-apple-darwin, macos-13)	2m 33s
release-dry-run / build (x86_64-pc-windows-msvc, windows-2019)	2m 38s
release-dry-run / build (x86_64-unknown-freebsd)	1m 51s
release-dry-run / build (universal-apple-darwin, macos-13)	3m 29s
	51m 41s

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