WPCOMSH: Removing duplicated functionality to remove masterbar module listing

[coder-karen]

On hold

This now may need to wait until the module itself is removed as it seems there may be a priority issue - the module is not disappearing from the modules page using this PR.

Fixes https://github.com/Automattic/vulcan/issues/448

Proposed changes:

• Once this PR was merged - https://github.com/Automattic/jetpack/pull/38804 - the 'masterbar' module no longer showed up on the Jetpack modules page. As such the function in wpcomsh/masterbar.php to do the same is not needed, and is removed in this PR.

Other information:

• [ ] Have you written new tests for your changes, if applicable?
• [ ] Have you checked the E2E test CI results, and verified that your changes do not break them?
• [ ] Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

https://github.com/Automattic/vulcan/issues/448

Does this pull request change what data or activity we track or use?

No.

Testing instructions:

• To test this out, the best option may be to use rsync on a WoA dev site: jetpack rsync wpcomsh - the path being /srv/htdocs/wp-content/plugins/wpcomsh-dev
• You may be able to use a WoA test site using the Beta tester plugin and checking out this branch but I was unable to change branches or even change to bleeding edge / RC on wpcomsh using the Beta Tester plugin
• Visit the modules page - wp-admin/admin.php?page=jetpack_modules - and you should not see any listing for the WordPress.com Toolbar (this is the 'masterbar' module).

[github-actions[bot]]

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[coder-karen]

Closing this as unneeded just now.