Instead of running dependabot on all the release branches

backport it's PRs from master

Author: HoloRin

.github/dependabot.yaml

@@ -6,18 +6,7 @@ updates:
     schedule:
       interval: "daily"
     target-branch: "master"
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "daily"
-    target-branch: "v3.10.x"
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "daily"
-    target-branch: "v3.9.x"
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "daily"
-    target-branch: "v3.8.x"
+    labels:
+      - backport-v3.10.x
+      - backport-v3.9.x
+      - backport-v3.8.x