Revert "configure: run plugin TCG tests again"

Revert "configure: run plugin TCG tests again"

This reverts commit 6eeeb8733177db7bc23fb2e7271dea759b47e4f9.

This commit has been wrongly back-ported to 8.2.x, $config_host_mak
in master didn't include the tests/tcg/ prefix, while 8.2.0 did it.
The result of this "backport" is this message during configure:

 ../configure: 1679: cannot create tests/tcg/tests/tcg/config-host.mak: Directory nonexistent

Let's revert the change and try again.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>