sdvx: remove -sdvxdisablecams, simplify camera hook (#350)

## Link to GitHub Issue, if one exists
#345

## Description of change
Simplify camera hook in SDVX5/6. Camera hook will always be installed
and return 0 cameras.

Deprecate `-sdvxdisablecams` option as it is no longer needed as a
result of this change.

## Testing
Tested SDVX5 final, SDVX6 year 1, and a recent SDVX6 build.

src/spice2x/launcher/launcher.cpp

@@ -433,9 +433,6 @@ int main_implementation(int argc, char *argv[]) {
     if (options[launcher::Options::LoadSoundVoltexModule].value_bool()) {
         attach_sdvx = true;
     }
-    if (options[launcher::Options::SDVXDisableCameras].value_bool()) {
-        games::sdvx::DISABLECAMS = true;
-    }
     if (options[launcher::Options::SDVXNativeTouch].value_bool()) {
         games::sdvx::NATIVETOUCH = true;
     }