Fix findPluginsToDownload falsely check installed version

[anhcraft]

I noticed that PluginManager#findPluginsToDownload has a wrong logic if-else. For a requested plugin, if there is both installed plugin and bundled plugin, then the method only gets the version from the installed one without checking if the bundled one is newer. The else logic was added in c445dea

Testing done

I have adjusted the test case to suit the new changes.

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