Docs: Minorly improve the hook doc summary for the `pre_uninstall_plugin`...

Docs: Minorly improve the hook doc summary for the `pre_uninstall_plugin` action, introduced in [36124].

See #34569. See #35986.

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git-svn-id: https://core.svn.wordpress.org/trunk@36791 1a063a9b-81f0-0310-95a4-ce76da25c4cd