Merge branch '21.0-ATLASRECTS-4062-firstParsFlag-bugFix' into '21.0'

Fix preInclude of BLS stream to keep only first measured parameters; ATLASRECTS-4062.

See merge request !2781

Reconstruction/RecExample/RecExCommon/share/preIncludeForBLSStream.py

 #This is a preInclude file to be used to run the BLS stream in production.
 #Author: James Walder
 from InDetRecExample.InDetJobProperties import InDetFlags
-InDetFlags.KeepParameters.set_Value_and_Lock(True)
+InDetFlags.KeepFirstParameters.set_Value_and_Lock(True)
 InDetFlags.keepAdditionalHitsOnTrackParticle.set_Value_and_Lock(True)
 InDetFlags.cutLevel.set_Value_and_Lock(13)