Fix editor underscore visibility on Linux systems

- seems to relate to DejaVu Sans font rendering
- fixes #2104

packages/node_modules/@node-red/editor-client/src/sass/ace.scss

@@ -52,6 +52,9 @@
         @include component-shadow;
         border-color: $popover-background;
     }
+    .ace_content {
+        line-height: 1;
+    }
     textarea.ace_text-input {
         overflow: hidden;
         padding: 0px 1px !important;