DAOS-19085 cq: retire the release/2.6.4-* branches

Retire these release branches now that 2.6.5 is released.

Doc-only: true

Signed-off-by: Dalton Bohning <dalton.bohning@hpe.com>

Author: daltonbohning

.github/dependabot.yml

@@ -55,31 +55,3 @@ updates:
       - daos-stack/actions-watchers
     commit-message:
       prefix: "Doc-only: true \n"
-
-  - package-ecosystem: github-actions
-    target-branch: release/2.6.4-aurora
-    directory: /
-    schedule:
-      interval: weekly
-    groups:
-      gha-versions:
-        patterns:
-          - "*"
-    reviewers:
-      - daos-stack/actions-watchers
-    commit-message:
-      prefix: "Doc-only: true \n"
-
-  - package-ecosystem: github-actions
-    target-branch: release/2.6.4-mfg
-    directory: /
-    schedule:
-      interval: weekly
-    groups:
-      gha-versions:
-        patterns:
-          - "*"
-    reviewers:
-      - daos-stack/actions-watchers
-    commit-message:
-      prefix: "Doc-only: true \n"