ci: fix submodule bump for tarantool-ee 2.10

This patch fixes the following issue: the submodule_update.yml workflow
always updated the tarantool submodule in the tarantool-ee repo to the
last commit from the `master` branch, even if it was tarantool-ee 2.10.
Now it is fixed.

NO_DOC=ci
NO_TEST=ci
NO_CHANGELOG=ci