Base: Remove "idle" priority note from SystemServer(5)

The "idle" priority was never meant to be exposed to userspace, as it's
only used by the kernel's internal idle thread.

Base/usr/share/man/man5/SystemServer.md

@@ -19,7 +19,7 @@ describing how to launch and manage this service.
 * `Executable` - an executable to spawn. If no explicit executable is specified, SystemServer assumes `/bin/{service name}` (for example, `/bin/WindowServer` for a service named `WindowServer`).
 * `Arguments` - a space-separated list of arguments to pass to the service as `argv` (excluding `argv[0]`). By default, SystemServer does not pass any arguments other than `argv[0]`.
 * `StdIO` - a path to a file to be passed as standard I/O streams to the service. By default, services inherit SystemServer's own standard I/O streams, which are normally set to `/dev/tty0`.
-* `Priority` - the scheduling priority to set for the service, either "idle", "low", "normal", or "high". The default is "normal".
+* `Priority` - the scheduling priority to set for the service, either "low", "normal", or "high". The default is "normal".
 * `KeepAlive` - whether the service should be restarted if it exits or crashes. For lazy services, this means the service will get respawned once a new connection is attempted on their socket after they exit or crash.
 * `Lazy` - whether the service should only get spawned once a client attempts to connect to their socket.
 * `Socket` - a path to a socket to create on behalf of the service. For lazy services, SystemServer will actually watch the socket for new connection attempts. An open file descriptor to this socket will be passed as fd 3 to the service.