Change line-height for all codemirror areas

To improve UX we decided to increase lineheight value from 1.2 to 1.4
so the code lines wouldn't look squeezed.

Author: lotrien

src/styles/common/overwrite.styl

@@ -3,7 +3,7 @@
 .react-codemirror2,
 .CodeMirror
   height: 100% !important
-  line-height: 1.2
+  line-height: 1.4
 
 .new-snippet .react-codemirror2,
 .new-snippet .CodeMirror