privacy: Mention that system apps can always use the camera/microphone
These toggles only apply to the portal system, so only restrict access
for sandboxed apps. System apps (installed without sandboxing into
/usr/bin) can always access these resources on typical distributions.
In future, perhaps integration with a MAC (like SELinux) could restrict access to the camera/microphone/GPS for system applications — but we invented sandboxing to avoid having to do that, so it seems unlikely that’s ever going to be implemented. If it is, this wording can change again.
Signed-off-by: Philip Withnall email@example.com