CI: fix Dependabot workflow for automating changesets

[maschad]

The last few master workflow runs have been failing as CI is trying to report the coverage without generating the coverage itself

There are security considerations to be had when elevating permissions and we should understands the risks fully before doing so IMO.

We need to determine what's the most appropriate way to give dependabot the relevant write permissions or if it may be more appropriate to use the @fuel-service-user to generate the changesets.