Only display inline run button on mobile

Author: gnestor

notebook/static/notebook/less/codecell.less

@@ -42,10 +42,6 @@ div.code_cell div.input_prompt {
     min-width: 11ex;
 }
 
-div.code_cell:hover div.input .run_this_cell {
-    visibility: visible;
-}
-
 @media (-moz-touch-enabled: 1), (any-pointer: coarse) {
     .run_this_cell {
         visibility: visible;