fix(ui): only render header dom node if needed (#9742)

### What?
The `<header>` dom node was rendering even if empty for group fields.
Causing extra margin to be added even if no label/description were
provided.

### Why?
If the field had no label, description or errors it would still render.

### How?
Wraps the header node in an additional condition that checks for label,
description or errors before rendering the node.

packages/ui/src/fields/Group/index.tsx

@@ -71,6 +71,7 @@ export const GroupFieldComponent: GroupFieldClientComponent = (props) => {
     >
       <GroupProvider>
         <div className={`${baseClass}__wrap`}>
+          {Boolean(Label || Description || label || fieldHasErrors) && (
             <div className={`${baseClass}__header`}>
               {Boolean(Label || Description || label) && (
                 <header>
@@ -96,6 +97,7 @@ export const GroupFieldComponent: GroupFieldClientComponent = (props) => {
               )}
               {fieldHasErrors && <ErrorPill count={errorCount} i18n={i18n} withMessage />}
             </div>
+          )}
           {BeforeInput}
           <RenderFields
             fields={fields}