Remove CHECKIN MEMINFO section from dumpstate

This change removes the call to 'dumpsys meminfo --checkin', as it was
added in ~2013 and seems to be unused. The meminfo checkin accounts for
almost all of the DUMP CHECKINS section duration (~6.5s on AOSP redfin).
Removing the meminfo checkin makes the DUMP CHECKINS duration
negligible (<250ms).

Test: Checked that bug reports no longer contain CHECKIN MEMINFO.
Bug: 239227919
Change-Id: Ia5e1df4f5a833353b48d18a3518a8bd293f49bef