Fix clippy driver stderr test

Author: flip1995

.github/driver.sh

@@ -30,7 +30,7 @@ unset CARGO_MANIFEST_DIR
 # Run a lint and make sure it produces the expected output. It's also expected to exit with code 1
 # FIXME: How to match the clippy invocation in compile-test.rs?
 ./target/debug/clippy-driver -Dwarnings -Aunused -Zui-testing --emit metadata --crate-type bin tests/ui/double_neg.rs 2>double_neg.stderr && exit 1
-sed -e "s,tests/ui,\$DIR," -e "/= help/d" double_neg.stderr >normalized.stderr
+sed -e "s,tests/ui,\$DIR," -e "/= help: for/d" double_neg.stderr > normalized.stderr
 diff -u normalized.stderr tests/ui/double_neg.stderr
 
 # make sure "clippy-driver --rustc --arg" and "rustc --arg" behave the same