Hello, The global function "wfWaitForSlaves()" that has been soft deprecated [1] since 1.27 is now hard deprecated (from master and subsequently 1.35 release) and will be removed soon.
Please use LBFactory::waitForReplication instead.
I would like to thank Sam Reed for cleaning up all of the usages in extensions. For more context, see https://phabricator.wikimedia.org/T181673
[1]: See Stable interface policy for the definitions: https://www.mediawiki.org/wiki/Stable_interface_policy
Have a nice day