Don't remove the filter on pre_comment_approved

[tellyworth]

A user writes:

In the function akismet_result_spam, there is a call to remove_filter on pre_comment_approved, which is the filter that is currently being applied. Dynamically removing a filter in this way breaks all filters that were scheduled to run after the current one. This is a known issue - see ​https://core.trac.wordpress.org/ticket/9968 . The result is that any plugins that had hooked filters onto pre_comment_approved to be run after Akismet, will not work.

Please see if you can fix this behaviour. You should be able to ensure the function runs only once by having a static variable instead.

[eoigal]

Fixed from 2.6

Using a static variable to ensure only called once rather than depend on removing the filter