TEST_DEPENDS_ALL was part of _UNIFIED_DEPENDS, so test-only
dependencies leaked into all-depends-list, missing,
clean-depends, fetch-recursive, deinstall-depends and the QA
checks, even though they are not needed to build, package or
install a port. It pollutes all the convenience -recursive targets
including poudriere options.
They are still installed by "make test" through the test-depends
target, which is now documented as well.
The motivation for this patch is the fact that many ports now
end up having chromium as part of their dependency list following
the new dependency needed to upgrade py-great-table
(15ce974d8e0560b8038db69598cdf68c52273e68)