Hide editor specific text area input inline help outside of editor

The inline help recommends "open in new tab" to prevent users from
having to reload the Pageflow entry. This only makes sense when
actually editing a Pageflow entry.

REDMINE-20511

app/assets/stylesheets/pageflow/ui/input/text_area_input.scss

@@ -174,4 +174,16 @@
     border-bottom: solid 9px var(--ui-surface-color);
     border-left: solid 9px transparent;
   }
+
+  // Hide inline help text that only makes sense when editing a
+  // Pageflow entry outside the editor
+  .open_in_new_tab_section .inline_help {
+    display: none;
+  }
+}
+
+.editor .text_area_input {
+  .open_in_new_tab_section .inline_help {
+    display: block;
+  }
 }