chore: improve dependabot config (temporalio#1044)

## What was changed
- Group all GitHub Actions updates into a single PR
- Ignore indirect Go dependencies (only direct deps get PRs)
- Ignore all `go.temporal.io/*` dependencies — these are managed
manually to ensure coordinated upgrades across all temporal packages

Author: chaptersix

.github/dependabot.yml

@@ -6,10 +6,19 @@ updates:
       interval: weekly
     cooldown:
       default-days: 14
+    ignore:
+      - dependency-name: "*"
+        dependency-type: indirect
+      # Temporal dependencies are managed manually to ensure coordinated upgrades across all temporal packages
+      - dependency-name: "go.temporal.io/*"
 
   - package-ecosystem: github-actions
     directory: "/"
     schedule:
       interval: weekly
     cooldown:
       default-days: 14
+    groups:
+      github-actions:
+        patterns:
+          - "*"