chore: upgrade release please action from v2 to v4

[ayushmanchhabra]

Checklist

• npm install && npm run lint && npm test passes
• commit message follows commit guidelines

Description of change

Upgrade Release Please action from v2 to v4.

Fixes: #2971

[ayushmanchhabra]

I can set the target-branch to this branch to test if the changes made work.

I did something similar in nw-builder and created a release from the PR as target branch.

[cclauss]

@DeeDeeG Your review, please.

[DeeDeeG]

This looks good to me overall.

I had only a couple of minor suggestions for changes, one of which is only a code style suggestion, but the other should keep our tag names consistent with what they have been since before release-please-action@v4.

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For context: I am doing this review after looking over this PR author's other PR doing similar: https://github.com/nwutils/nw-builder/pull/1032/files ...And the implementation they said they looked at for reference: https://github.com/mdn/yari/commits/main/release-please-config.json... And the official config file schema for the latest release-please version: https://github.com/googleapis/release-please/blob/3569f158158e2bd096a94c145bdb1a7f455829f0/schemas/config.json

This seems to be a valid configuration that should work with release-please-action@v4.

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Thank you @ayushmanchhabra for doing this!

[DeeDeeG]

Thanks again!

[DeeDeeG]

Re-approve after indentation change. (Thanks!)

[lukekarrys]

I don't think last-release-sha is necessary since Release Please should pick up the latest release automatically. I am going to merge this without that change and see if the Release PR looks correct. If not I will make another PR adding this back in.