PortingPolicy, TestFailures: make port-maintainers links more direct

Link directly to the 'Teams' tab instead of the default 'Members' tab.
It's more useful, since the top-level golang/port-maintainers team is
not really used; it just holds the port-specific sub-teams.

The link at https://go.dev/wiki/PortingPolicy#maintaining-a-port
already does this, and this CL updates the other two.

Change-Id: I3c0167089f809345e7afd6fe786739e19cc6d2f0
Reviewed-on: https://go-review.googlesource.com/c/wiki/+/767942
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>