docs: add NEWS entry for vignette fix and create follow-up issue

Add NEWS.md entry for the approx inference vignette re-enablement.
Created #592 to track removing brms from Remotes once CRAN catches up.

Co-authored-by: Sam Abbott <contact@samabbott.co.uk>

Author: seabbs-bot

NEWS.md

@@ -7,6 +7,8 @@
   the marginal model. See #583.
 - Added `primarycensored (>= 1.4.0)` version bound to DESCRIPTION.
 - Updated test expectations for changed primarycensored error handling.
+- Re-enabled approximate inference vignette evaluation using dev brms with
+  pathfinder path fix. See #579.
 
 ## CI