Documentation error for activate_plugin hook

[wedi]

The documentation for the activate_plugin hook is erroneous. In the beginning it says that the hook gets fired on plugin deactivation. When you read further it suddenly says activation. This is probably a simple copy&paste error.

https://core.trac.wordpress.org/browser/trunk/src/wp-admin/includes/plugin.php#L560

My original report for reference: ​https://meta.trac.wordpress.org/ticket/606

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While investigating, @georgestephanis noticed a bad reference here:

https://core.trac.wordpress.org/browser/trunk/src/wp-admin/plugins.php#L154

It should refer to wp-admin/includes/plugin.php -- not plugins.php -- no s.

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The attached patch fixes both issues.

[SergeyBiryukov]

The first part was introduced in [27769] and fixed in [29977].

The second part was introduced in [26345].

[SergeyBiryukov]

In 30117:

Use correct file name in a hook comment.

props wedi.
fixes #30200.