Revert "MM-55295: Improve DB performance of some APIs (#25318)" (#25852)

This reverts commit ec88ab4ee9.

server/channels/app/channel.go

@@ -2063,21 +2063,6 @@ func (s *Server) getChannelMember(c request.CTX, channelID string, userID string
 	return channelMember, nil
 }
 
-func (s *Server) getChannelMemberOnly(c request.CTX, channelID string, userID string) (*model.ChannelMember, *model.AppError) {
-	channelMember, err := s.Store().Channel().GetMemberOnly(c.Context(), channelID, userID)
-	if err != nil {
-		var nfErr *store.ErrNotFound
-		switch {
-		case errors.As(err, &nfErr):
-			return nil, model.NewAppError("getChannelMemberOnly", MissingChannelMemberError, nil, "", http.StatusNotFound).Wrap(err)
-		default:
-			return nil, model.NewAppError("getChannelMemberOnly", "app.channel.get_member.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
-		}
-	}
-
-	return channelMember, nil
-}
-
 func (a *App) GetChannelMembersPage(c request.CTX, channelID string, page, perPage int) (model.ChannelMembers, *model.AppError) {
 	channelMembers, err := a.Srv().Store().Channel().GetMembers(channelID, page*perPage, perPage)
 	if err != nil {