Remove unneeded set_time_limit() calls from network/sites.php

[dllh]

A call to set_time_limit() was introduced in ​http://mu.trac.wordpress.org/changeset/860/trunk/wp-admin/wpmu-edit.php and has made its way into wp-admin/network/sites.php. Since the call is adjacent to spam actions that could make a network call to akismet that could take some time to return, its intention is presumably to allow the code enough time to execute without timing out even if the network call takes a while.

But set_time_limit() won't take network time into account, so it actually will not do what it seems designed to do. From php docs:

The set_time_limit() function and the configuration directive max_execution_time only affect the execution time of the script itself. Any time spent on activity that happens outside the execution of the script such as system calls using system(), stream operations, database queries, etc. is not included when determining the maximum time that the script has been running.

Further, calls to set_time_limit() can cause unexpected results in code that relies on any functions that call set_time_limit(). For example, if some code (in a cron job, say) sets the time limit to 0 (unlimited) because it knows it needs some time complete, then a subsequent call to a function that resets the time limit will halt the long-running execution once the new limit has been reached. Also from php docs:

When called, set_time_limit() restarts the timeout counter from zero. In other words, if the timeout is the default 30 seconds, and 25 seconds into script execution a call such as set_time_limit(20) is made, the script will run for a total of 45 seconds before timing out.

Since the call to set_time_limit() does not here do anything useful, it should be removed.

[dllh]

Removes unneeded calls to set_time_limit()

[kurtpayne]

Related #19487

[ryan]

In [22259]:

Remove set_time_limit() from sites.php. Props dllh. fixes #19486 see #21521