bug#30279: Where is image-dired-thumb-job-limit?

[Juri Linkov]

>> Noticed when reading NEWS.26 image-dired-thumb-job-limit is mentioned,
>> but nowhere is defined.  Closest variable that can be found in image-dired
>> is image-dired-queue-active-limit.  Should the former be replaced with 
>> latter?
>
> Since image-dired-queue-active-limit is not a defcustom, I'd say the
> reference to it should be simply removed.

I hesitated to remove it because it will help the users to know the source
of a possible problem (e.g. concurrent processes taking too much CPU).

> (But if you see this in NEWS.26, you are in the wrong branch to edit
> that file.)

I renamed it in the right branch.