Fix deprecation notice for ble::Gap::getState()
Fix deprecation notice for ble::Gap::getState()

The deprecation notice suggests getConnectionCount() which
did not land in the final API. The proper replacement is keeping
your own record and updating during connection and disconnection
callbacks.

kjbracey-arm/mbed,mbedmicro/mbed,mbedmicro/mbed,andcor02/mbed-os,andcor02/mbed-os,andcor02/mbed-os,kjbracey-arm/mbed,kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,mbedmicro/mbed,andcor02/mbed-os