Update RHCOS to OCP version map (#3298)

Co-authored-by: sebrandon1 <[email protected]>

Author: github-actions[bot]

tests/platform/operatingsystem/files/rhcos_version_map

@@ -651,6 +651,7 @@
 4.20.0-rc.1 / 9.6.20250908-0
 4.20.0-rc.2 / 9.6.20250909-0
 4.20.0-rc.3 / 9.6.20250925-0
+4.20.1 / 9.6.20251021-0
 4.21.0-ec.0 / 9.6.20250904-0
 4.21.0-ec.2 / 9.6.20251017-0
 4.4.0 / 44.81.202004260825-0