upgrade: Drop unnecessary memcached restart.
upgrade: Drop unnecessary memcached restart.

The contents in the database are unchanged across the PostgreSQL
restart; as such, there is no reason to invalidate the caches.

This step was inherited from the general operating system upgrade
documentation.  When Python versions change, such as during OS
upgrades, we must ensure that memcached is cleared.  However, the
`do-release-upgrade` process uninstalled and upgraded to a new
memcached, as well as likely restarted the system; a separate step for
OS upgrades to restart memcached is thus unnecessary.

showell/zulip,andersk/zulip,showell/zulip,eeshangarg/zulip,hackerkid/zulip,punchagan/zulip,showell/zulip,showell/zulip,punchagan/zulip,punchagan/zulip,eeshangarg/zulip,zulip/zulip,zulip/zulip,kou/zulip,kou/zulip,rht/zulip,hackerkid/zulip,rht/zulip,kou/zulip,rht/zulip,brainwane/zulip,hackerkid/zulip,zulip/zulip,zulip/zulip,kou/zulip,brainwane/zulip,zulip/zulip,showell/zulip,punchagan/zulip,punchagan/zulip,rht/zulip,hackerkid/zulip,zulip/zulip,brainwane/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,hackerkid/zulip,showell/zulip,punchagan/zulip,brainwane/zulip,rht/zulip,andersk/zulip,andersk/zulip,brainwane/zulip,hackerkid/zulip,kou/zulip,andersk/zulip,andersk/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,eeshangarg/zulip,punchagan/zulip,andersk/zulip,kou/zulip,andersk/zulip,hackerkid/zulip,brainwane/zulip,rht/zulip,eeshangarg/zulip,brainwane/zulip,showell/zulip