Back in 2015 we set the max entity size based on the largest revision at the time.
https://github.com/wikimedia/operations-mediawiki-config/commit/968516d4638448a1992498ca173c3ba92dcf1994
This was due to us having severe UI issues at the time.
Now we want to Set maxSerializedEntitySize to 3000, to allow slightly larger entities, as some are again reaching the limit that we set 4 years ago (T215380)