[FUI23] Remove getNetworkQuotaInfo

Currently, getNetworkQuotaInfo in NetworkPolicyManagerService
uses NetworkState class, which will not be available after
ConnectivityService moved to mainline module.

Thus, to remove the usage of NetworkState, remove this function
since:
  1. There is no internal usage and the function only prints
     debug log.
  2. It is non-SDK API which annotated with maxTargetSdk = 30,
     callers should not expect it will continoue to work in next
     Android release.
  3. go/nonsdk-dash shows zero usage statistics.

Test: TH
Bug: 174123988
Change-Id: I450964a692b85f3ba89bf9f847e8089ee2445bda