Revert "Test(GridLayer): add 2 new tests for zoom-in/-out in graphical browsers (#6201)" (#6221)
Revert "Test(GridLayer): add 2 new tests for zoom-in/-out in graphical browsers (#6201)" (#6221)

For some reason these test pass fine in PR Travis CI, but fail most of the time in Master Build Travis CI (see also https://github.com/Leaflet/Leaflet/pull/6207). Since they are just extra tests, we can happily remove them for now. If the root cause is found later on, it will be easy to merge them back.

This reverts commit 380c44fe04b3d8f584ce2277ba74c30c8c810bdc.
Leaflet/Leaflet,CapeSepias/Leaflet,Leaflet/Leaflet,stefanocudini/Leaflet,stefanocudini/Leaflet,CapeSepias/Leaflet,Leaflet/Leaflet,CapeSepias/Leaflet,stefanocudini/Leaflet