Improved docs on accept_mutex_delay

[muhammedsirajudeen]

Proposed changes

While reading the docs especially the accept_mutex_delay section the sentence there bugged me quiet a bit. So I just added two words that would make reading that it a bit more easier

If [accept_mutex](https://nginx.org/en/docs/ngx_core_module.html#accept_mutex) is enabled, specifies the maximum time during which a worker process will try to restart accepting new connections if another worker process is currently accepting new connections.

to

If [accept_mutex](https://nginx.org/en/docs/ngx_core_module.html#accept_mutex) is enabled, **this directive** specifies the maximum time during which a worker process will try to restart accepting new connections if another worker process is currently accepting new connections.

Part of documentation

I know this is isnt a big deal but it kinda bugged me a lot while reading it.

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[pluknet]

It is a fairly common wording in nginx; taking even the next directive(s) after it in the list:

<directive name="daemon">
...
Determines whether nginx should become a daemon.

<directive name="debug_connection">
...
Enables debugging log for selected client connections.

<directive name="load_module">
...
Loads a dynamic module.

accept_mutex_delay fits in quite well with them, up to the clarifying phrase in the beginning.

Adding "this directive" to all of them would make a small clarification benefit;
on the other side, this will compromise the compactness of the text wording.
I'd rather not, thanks.