ci: Switch PR merge strategy to rebase

Updates the GitHub Actions workflow to use a rebase merge strategy
instead of squash when merging automated pull requests.
This preserves individual commits from feature branches, ensuring
a linear and more granular commit history for data updates.

Author: MuhammadZeshan382

.github/workflows/update-currency-data.yml

@@ -112,4 +112,4 @@ jobs:
           GH_TOKEN: ${{ github.token }}
           PR_NUMBER: ${{ steps.cpr.outputs.pull-request-number }}
         run: |
-          gh pr merge --auto --squash --delete-branch "$PR_NUMBER"
+          gh pr merge --auto --rebase --delete-branch "$PR_NUMBER"