webperf/deprecate: Log jqmigrate to statsd under mw.js.deprecate

See also:
- I6c868f2ce (mediawiki-core) Add mw.track( 'jquery.migrate' )
- I217f5d514 (mwext-WikimediaEvents) Subscribe to 'jquery.migrate'

Change-Id: Ib4482ebbb0e4b566f12fbbfdf7e3407a53c0663b
Merge "webperf/deprecate: Log jqmigrate to statsd under mw.js.deprecate" into production