Revert EXCLUDED_ROUTES to only keep RTN_UNICAST

Revert the previous change to filter out all non-RTN_THROW routes when
EXCLUDED_ROUTES is disabled, as that behavior is CTS tested for T, and
has been used by T for a while. The previous change already ensured that
there is no behavior change on S, so this is the safest approach.

This fixes HostsideLinkPropertiesGatingTests.

Bug: 239046959
Test: atest LinkPropertiesTest CtsHostsideNetworkTests
Change-Id: I55e078cdc06341f4957fe7bc743c0022b2c7d3da