🐛 Fix line-height of the indent-guide

Issue #4279

static/text-editor-light.less

@@ -155,6 +155,7 @@ atom-text-editor {
   }
 
   .indent-guide {
+    display: inline-block;
     box-shadow: inset 1px 0;
   }
 

static/text-editor-shadow.less

@@ -138,6 +138,7 @@
 }
 
 .indent-guide {
+  display: inline-block;
   box-shadow: inset 1px 0;
 }