Make lint script run clang-format against main (#8399)

Because this script first checks that there are no uncommitted changes,
this line was actually doing nothing as it was comparing against the
default HEAD.
diff --git a/scripts/lint.sh b/scripts/lint.sh
index 4bff737..89894ff 100755
--- a/scripts/lint.sh
+++ b/scripts/lint.sh
@@ -98,7 +98,7 @@
 disable_update_ret
 if exists git-clang-format; then
   enable_update_ret
-  git-clang-format --style=file
+  git-clang-format --style=file main
   git diff --exit-code
 else
   enable_update_ret