autopkgtest: Re-enable unbind-unbound-slot-luks2

Seems the timing issues are gone.

debian/tests/run-testsuite

@@ -26,10 +26,6 @@ exit=0
 cd "$src_dir/src/luks/tests"
 
 for f in $(find . -type f -not -name 'tests-common-functions*' -executable | sort); do
-    if [ "$f" = './unbind-unbound-slot-luks2' ]; then
-        echo "W: Skipping test $f"
-        continue
-    fi
     echo "I: Running test $f"
     # test are very noisy, keep them silent as long as they pass
     t0="$(date +%s)"