Merge "UpstreamNetworkMonitor: remove unused mTetheringUpstreamNetwork" am: 42d28f1d66

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2383987

Change-Id: I0d159b714a6a4ad46511c685588bb3f262e74bc9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>