test: bump test-run to version w/ updated luatest

Bump test-run to new version with the following improvements:

- Bump luatest to 0.5.7-33-g8523e5c [1]

[1] tarantool/test-run@7db594d

Part of tarantool/luatest#296

NO_DOC=testing stuff
NO_TEST=testing stuff
NO_CHANGELOG=testing stuff

(cherry picked from commit 80238639)

test-run @ 7db594df

-Subproject commit 7729a4c1de788b9dcaa99d99194839c15b49ae2e
+Subproject commit 7db594df5d336e940a9940a68b11d113d44e9c97