Plugin not properly uninstalled after SSH related tests completes

[jeawhanlee]

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Describe the bug
When we run tests, at the end of the test, we delete the WPR directory directly which does not perform the necessary clean up of the plugin.

To Reproduce
Steps to reproduce the behavior:

1. Run a test that depends on the SSH
2. Wait for test to finish
3. WPR is deleted from the list of plugins
4. Check the DB and see that the transients and WPR related tables are still there.

Expected behavior
We need to uninstall the plugin properly so that the required hooks responsible for clearing the plugin data is fired.

Screenshots
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Additional context
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Acceptance Criteria (for WP Media team use only)
Clear instructions for developers, to be added before the grooming

[jeawhanlee]

Closing as it's already addressed in this PR