Revert "[CI][format] Explicitly pass extensions to git-clang-format (#95794)"

This reverts commit 7620fe0d2d.

This patch was causing some significant portion of code formatting jobs
to succeed when they should have failed. More investigation is needed.

Tracked in #97060.

llvm/utils/git/code-format-helper.py

@@ -216,17 +216,6 @@ class ClangFormatHelper(FormatHelper):
             cf_cmd.append(args.start_rev)
             cf_cmd.append(args.end_rev)
 
-        # Gather the extension of all modified files and pass them explicitly to git-clang-format.
-        # This prevents git-clang-format from applying its own filtering rules on top of ours.
-        extensions = set()
-        for file in cpp_files:
-            _, ext = os.path.splitext(file)
-            extensions.add(
-                ext.strip(".")
-            )  # Exclude periods since git-clang-format takes extensions without them
-        cf_cmd.append("--extensions")
-        cf_cmd.append("'{}'".format(",".join(extensions)))
-
         cf_cmd.append("--")
         cf_cmd += cpp_files