Assign area:builds to version bump PRs (#8205)

## Summary of changes

This PR assigns the label area:builds to version bump PRs.

## Reason for change

During releases, version bump PRs are created and they have no label,
which makes the workflow add-labels to fail. It's not a big deal, we can
manually add a proper label and rerun the workflow, but it's better if
we do that automatically.

## Implementation details

## Test coverage

## Other details
<!-- Fixes #{issue} -->


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Author: NachoEchevarria

.github/labeller.yml

@@ -47,6 +47,9 @@ labels:
   - name: "area:builds"
     title: "^\\[?(?i)build"
 
+  - name: "area:builds"
+    title: "^\\[?(?i)(version bump)"
+
   - name: "area:ssi"
     title: "^\\[?(?i)(fleet installer)"