Revert "[build]: disable unit tests for sonic-utilities" (#6598)

This reverts commit 470ed18a6b.

rules/sonic-utilities.mk

@@ -13,5 +13,4 @@ $(SONIC_UTILITIES_PY3)_DEBS_DEPENDS = $(LIBYANG) \
                                       $(LIBYANG_PY3) \
                                       $(LIBSWSSCOMMON) \
                                       $(PYTHON3_SWSSCOMMON)
-$(SONIC_UTILITIES_PY3)_TEST = n
 SONIC_PYTHON_WHEELS += $(SONIC_UTILITIES_PY3)