GRN2-xx: Allowed file types now matches BigBlueButton (#1966)

* Allowed file types now matches BigBlueButton

* Uppercased file types are now allowed

* Rubocop

spec/controllers/rooms_controller_spec.rb

@@ -821,7 +821,7 @@ describe RoomsController, type: :controller do
     before do
       @user = create(:user)
       @file = fixture_file_upload('files/sample.pdf', 'application/pdf')
-      @invalid_file = fixture_file_upload('files/invalid.jpg', 'image/jpg')
+      @invalid_file = fixture_file_upload('files/invalid.bmp', 'image/bmp')
       allow(Rails.configuration).to receive(:preupload_presentation_default).and_return("true")
     end