add missing documentation

src/com/AircraftReporter.cpp

@@ -79,7 +79,7 @@ bool AircraftReporter::send(const aman::AircraftReport& report) {
     return retval;
 }
 
-AircraftReporter& AircraftReporter::instance() {
+AircraftReporter& AircraftReporter::instance() noexcept {
     static AircraftReporter __instance;
     return __instance;
 }