Crash on iOS [ODWLogManager flushAndTeardown]

[denny-msft]

iOS ODWReachability::stopNotifier is missing a return causing a crash on tear down.

Module	Function / Method	File	Line
libsystem_pthread.dylib	pthread_mutex_lock$VARIANT$armv81	—	—
SystemConfiguration	SCNetworkReachabilitySetCallback	—	—
Telemetry	-[ODWReachability stopNotifier]	ODWReachability.m	367
Telemetry	-[ODWReachability dealloc]	ODWReachability.m	265
Telemetry	Microsoft::Applications::Events::PlatformAbstraction::NetworkInformation::~NetworkInformation()	NetworkInformationImpl.mm	102
Telemetry	_ZNSt3__110shared_ptrIN9Microsoft12Applications6Events15ITaskDispatcherEEaSB8ne180100EOS5_	shared_ptr.h	157
Telemetry	Microsoft::Applications::Events::PlatformAbstraction::PlatformAbstractionLayer::shutdown()	PAL.cpp	626
Telemetry	Microsoft::Applications::Events::LogManagerImpl::FlushAndTeardown()	PAL.hpp	215
Telemetry	Microsoft::Applications::Events::LogManagerBase<Microsoft::Applications::Events::ModuleLogConfiguration>::FlushAndTeardown()	LogManagerBase.hpp	290
Telemetry	+[ODWLogManager flushAndTeardown]	ODWLogManager.mm	267

Introduced in #1323 with v3.9.163.1

[denny-msft]

The more critical issue is that ODWReachability shouldn't even be called on higher iOS versions. The bug is in NetworkInformationImpl initializing the reachability class without an availability check. However, given the EOL for iOS 11 and macOS 10.14, we can just remove references to ODWReachability.