Handle miscounting of coalesced changes in client recent changes

This normalises the count of coalesced changes.

In several months, the "normalisation" can be removed as such entries
will eventually be purged from recent changes table on Wikidata.

Bug: 45812
Change-Id: I4c82c610d2316450451fe97d0f490e0342f9d4e9
Merge "Handle miscounting of coalesced changes in client recent changes"