nfc(api): Dont invoke enableReaderMode from setDiscoveryTech

Calling |enableReaderMode| prevents us from chaning the listen tech.

Bug: 337291737
Test: atest CtsNfcHceMultiDeviceTestCases
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:c1eec317f5d98181e7ef8826a16c96ebebd9d498)
Merged-In: Id6a5e865cd69bafcf2e0dcfafe104aee3330f138
Change-Id: Id6a5e865cd69bafcf2e0dcfafe104aee3330f138