Force branch overwrite in metadata nightly job

[jaydeluca]

Fixes https://github.com/open-telemetry/opentelemetry-java-instrumentation/actions/runs/18702650904/job/53334377239

Run BRANCH_NAME="otelbot/metadata-update-main"
8258f601d86096c2b57e15a33fe766b5542852a5	refs/heads/otelbot/metadata-update-main
From https://github.com/open-telemetry/opentelemetry-java-instrumentation
 * branch                  otelbot/metadata-update-main -> FETCH_HEAD
 * [new branch]            otelbot/metadata-update-main -> origin/otelbot/metadata-update-main
error: Your local changes to the following files would be overwritten by checkout:
	docs/instrumentation-list.yaml
Please commit your changes or stash them before you switch branches.
Aborting

Also adding a notification for when this fails in the future