Remove unused prefixes, add unprefixed styles (Leaflet#6282)

Added `cursor: grabbing`, leaving `cursor: move` in as internet explorer does not support `grabbing` (nor the vendor-prefixed versions).

Removed `-o-transform` and `-o-transition`

dist/leaflet.css

@@ -169,7 +169,6 @@
 	opacity: 0;
 	-webkit-transition: opacity 0.2s linear;
 	   -moz-transition: opacity 0.2s linear;
-	     -o-transition: opacity 0.2s linear;
 	        transition: opacity 0.2s linear;
 	}
 .leaflet-fade-anim .leaflet-map-pane .leaflet-popup {
@@ -186,14 +185,12 @@
 .leaflet-zoom-anim .leaflet-zoom-animated {
 	-webkit-transition: -webkit-transform 0.25s cubic-bezier(0,0,0.25,1);
 	   -moz-transition:    -moz-transform 0.25s cubic-bezier(0,0,0.25,1);
-	     -o-transition:      -o-transform 0.25s cubic-bezier(0,0,0.25,1);
 	        transition:         transform 0.25s cubic-bezier(0,0,0.25,1);
 	}
 .leaflet-zoom-anim .leaflet-tile,
 .leaflet-pan-anim .leaflet-tile {
 	-webkit-transition: none;
 	   -moz-transition: none;
-	     -o-transition: none;
 	        transition: none;
 	}
 
@@ -226,6 +223,7 @@
 	cursor: move;
 	cursor: -webkit-grabbing;
 	cursor:    -moz-grabbing;
+	cursor:         grabbing;
 	}
 
 /* marker & overlays interactivity */
@@ -496,7 +494,6 @@
 	-webkit-transform: rotate(45deg);
 	   -moz-transform: rotate(45deg);
 	    -ms-transform: rotate(45deg);
-	     -o-transform: rotate(45deg);
 	        transform: rotate(45deg);
 	}
 .leaflet-popup-content-wrapper,