gifn-apply: Ruff preview mode: SPDX, subprocess

Enable Ruff's preview mode.
Specify a regular expression to check for copyright notices that
will match our SPDX tags.
Override another "subprocess is insecure" warning.

Ruff: CPY001,S404
Change-Id: I47e11e6c8269b92e68ea51659a9e790d3ef9315e
diff --git a/tools/git-if-needed/python/gifn_apply/git.py b/tools/git-if-needed/python/gifn_apply/git.py
index f19efab..8650fd6 100644
--- a/tools/git-if-needed/python/gifn_apply/git.py
+++ b/tools/git-if-needed/python/gifn_apply/git.py
@@ -4,7 +4,7 @@
 
 from __future__ import annotations
 
-import subprocess
+import subprocess  # noqa: S404
 
 from typing import TYPE_CHECKING