[INTERNAL][FIX] sap.m.MenuButton: unit tests are now passing
[INTERNAL][FIX] sap.m.MenuButton: unit tests are now passing

Using "sap/ui/qunit/utils/waitForThemeApplied" module
in order to apply the css theme before starting of the tests.

Change-Id: Id09a2f220a496500c6320437e2aad89485e96824
BCP: 1970006159

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5