Plugins sub-menu has wrong name under multisite site admin
|Reported by:||kawauso||Owned by:||ryan|
 introduced new sub-menu labels such as "All <x>" and "Installed Plugins", but under multisite the Plugins sub-menu has no other items and the label for the plugins page in the sub-menu is auto-generated from the parent.
In short, the label becomes just "Plugins" rather than "Installed Plugins" as on single site installs.
Steps to Reproduce:
- Activate Akismet or other plugin that adds a sub-menu item under the Plugins sub-menu
- Look at Plugins sub-menu