The Plug-Ins installer was part of Revoice Pro 2 on OS X.
Revoice Pro 3 and 4 install all plug-ins when the standalone application is launched for the first time; there is no separate installer.
On these versions, the standalone app must be opened at least once before you open your digital audio workstation.
Revoice Pro 5 uses a single installer for app and plug-ins instead.