fix custom-field-stringtemplate-separator string

i18n/en.i18n.json

@@ -991,5 +991,5 @@
   "moveSwimlanePopup-title": "Move Swimlane",
   "custom-field-stringtemplate": "String Template",
   "custom-field-stringtemplate-format": "Format (use %{value} as placeholder)",
-  "custom-field-stringtemplate-separator": "Separator (use   or   for a space)"
+  "custom-field-stringtemplate-separator": "Separator (use   or   for a space)"
 }