chore: eol support for 3.1.x (#1627)

* chore: eol support for 3.1.x

End of life support for 3.1.x branch as of 2021-12-17.
This change removes the configuration for this branch.

* 🦉 Updates from OwlBot

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

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

Author: thiagotnunes

.github/release-please.yml

@@ -2,10 +2,6 @@ releaseType: java-yoshi
 bumpMinorPreMajor: true
 handleGHRelease: true
 branches:
-  - branch: 3.1.x
-    releaseType: java-yoshi
-    bumpMinorPreMajor: true
-    handleGHRelease: true
   - branch: 3.3.x
     releaseType: java-yoshi
     bumpMinorPreMajor: true

.github/sync-repo-settings.yaml

@@ -20,21 +20,6 @@ branchProtectionRules:
       - compile (8)
       - compile (11)
       - OwlBot Post Processor
-  - pattern: 3.1.x
-    isAdminEnforced: true
-    requiredApprovingReviewCount: 1
-    requiresCodeOwnerReviews: true
-    requiresStrictStatusChecks: false
-    requiredStatusCheckContexts:
-      - dependencies (8)
-      - dependencies (11)
-      - lint
-      - units (7)
-      - units (8)
-      - units (11)
-      - 'Kokoro - Test: Integration'
-      - cla/google
-      - checkstyle
   - pattern: 3.3.x
     isAdminEnforced: true
     requiredApprovingReviewCount: 1