fix(docs): trigger update-docs workflow when the release-please PR gets merged and not on every merge to master

[kevaundray]

Description

Currently we are triggering the update-docs workflow when there is a change on the release-please PR branch, this is okay for workflows like update-lockfile. However, it doesn't work for update-docs because it uses needs.release-please.outputs.release-tag-name which depends on the release-please tag which we get after we have merged the release-please PR into master.

See here for example where update lockfile is ran on master.

Problem*

Resolves

Summary*

Additional Context

Documentation*

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• No documentation needed.
• Documentation included in this PR.
• [Exceptional Case] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.