Replace usage of wpua_hash_gravatar in wp_options

An additional update from them:

So one quick “fix” would be to have the option not saved into the alloptions array, setting the third parameter to false during update_option(). In these locations: https://github.com/wpcomvip/ona-journalists/blob/ecf93e386046e34856c2e32b7a38681333f459c9/plugins/wp-user-avatar/includes/class-wp-user-avatar-functions.php#L225-L247

This will keep it from running the alloptions cache above 1mb. This is not perfect, as it means that the wpua_hash_gravatar option will have to be fetched separately from memcache each request it is used – and if it’s above 1MB it will be unable to be served by memcache for the same reasons as alloptions. But this is a better scenario than alloptions being above 1MB as it is requested substantially more times.

This has been fixed in the upcoming update.