Revert "tests/tcg: skip the vma-pthread test on CI"

Now that the page_check_range() race condition is fixed, let
vma-pthread run on CI again.

This reverts commit 5842de51573fdbd7299ab4b33d64b7446cc07649.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20260706165445.57418-4-iii@linux.ibm.com>