Update Flow to wmf/1.24wmf2

Updates embedded $wgFlowCacheVersion to match mediawiki-config
repository.

Patches applied:
* I3c32d79d74a59abfe155174aa314250f1fe2a02a

Change-Id: Ifc3fc8542134866ff9eba5d3f5ae68d162ba0048
Merge "Update Flow to wmf/1.24wmf2" into wmf/1.24wmf2