Fix part of #7450: Replaced private methods in SuggestionServicesUnitTests (#15001)
Fix part of #7450: Replaced private methods in SuggestionServicesUnitTests (#15001)

Co-authored-by: Gopi Vaibhav <700b479eeba3ad54f6b513b2f403e3fe4af4cef3@pop-os.localdomain>
oppia/oppia,brianrodri/oppia,oppia/oppia,brianrodri/oppia,oppia/oppia,brianrodri/oppia,oppia/oppia,oppia/oppia,brianrodri/oppia,brianrodri/oppia