Updated mediawiki/extensions
Project: mediawiki/extensions/Flow  99a309feab435d51b43ab85e157875f1cc9f8a73

Drop table: flow_header_revision

Remove maintenance update to flow_header_revision as well. Since jenkins
creates flow table for unittest from scratch, it would cause error when
updating a non-existing table

Change-Id: I1af9d1bf5014f84a529de9ad017f14a813b79896