Remove unsupported NetworkManagement AIDL methods

These methods will always crash the caller and so do not serve any
purpose.

Flag: EXEMPT refactor

Test: Existing tests unaffected.

Bug: 339532486
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:4cbacfd0397cce814f12e93b3d3baf9c37155bb8)
Merged-In: I05514790e05e779777ed6f7b1b2f87479012b202
Change-Id: I05514790e05e779777ed6f7b1b2f87479012b202