Remove subIds from Telephony NetworkRequests.

Since NetworkProviders do not at present support requests with subIds
(they always provide an empty list, therefore never have an overlap),
the TelephonyBringupRequests must never present subIds as part of the
requested capabilities.

Bug: 183174340
Test: atest FrameworksVcnTests
Change-Id: I2e52ff67748c0ca226a648682b37dfe0996cb850