chore(python): remove configure_previous_major_version_branches (#2615)

chore(python): remove configure_previous_major_version_branches from python post processor

Source-Link: googleapis/synthtool@6702a34
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest@sha256:bb3dc6c75c5f3e1a8928474f2dc8d9bbfa7b809045515764b9ff48c070cf2321

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Jeff Ching <chingor@google.com>

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -1,4 +1,4 @@
-# Copyright 2023 Google LLC
+# Copyright 2025 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest
-  digest: sha256:bfe4592953269bfa8d135200ca1b17809f106a337a885d7ecc12cd2a9998e98a
-# created: 2023-11-15T20:00:24.246072277Z
+  digest: sha256:bb3dc6c75c5f3e1a8928474f2dc8d9bbfa7b809045515764b9ff48c070cf2321
+# created: 2025-11-03T16:03:37.116278509Z