jobqueue: Document Title as valid param type for compat (2)

jobqueue: Document Title as valid param type for compat (2)

Follows-up 9b4938c40d02c, and 4bff6f1558. The latter of which
updated ::factory() instead of __construct(). Oops.

This should fix build failures that are preventing merges
in repos where Phan is finding Job::__construct(string, Title)
where it currently fails as follows:

 CompileArticleMetadataJob.php:11
 PhanTypeMismatchArgument Argument 2 (params) is …\Title|string but
 \Job::__construct() takes array

As Phan is reading the php doc I guess.

Change-Id: I128d57ead6bcb9dbae99d41a1f23192c3f6fbdba