Fix release-tag trigger in infra pipeline definition files

[angela-tran]

The glob pattern we're using for release tags in azure-pipelines.yml is too permissive - 20??.??.?* matches more than just release tags.

We should update our trigger pattern in MST's pipeline and SBMTD's pipeline.

Originally posted by @angela-tran in #286 (comment)

[thekaveman]

This consequences of this are relatively minor, we can always create new tags at the correct SHA as-needed.