Fixes #1269 - RSSI Tx should be hidden in companion if radio is Taranis.

I followed isTelemetrySourceAvailable() and hided RssiTx and dTE.
Merge pull request #1284 from opentx/projectkk2glider/issue_1269

Fixes #1269 - RSSI Tx should be hidden in companion if radio is Taranis.