AOSP code has never used this API, and metrics from production
show no usage either. Removing it will allow simplifying the
code.
This CL removes testRequestStaticIpLegacyTether because it makes
legacyTether a no-op and there is already a test for static IP
request right above it.
Bug: 408087033
Flag: EXEMPT dead code
Test: updated existing tests
Change-Id: Ib94ed0860ab57abfd9fc7bdfdc911f5ab57003ed
bec4b5b8d4