Consistent learn more formatting

Signed-off-by: Adam Harvey <adam.harvey@dxc.com>

plugins/catalog/src/components/HasComponentsCard/HasComponentsCard.tsx

@@ -76,7 +76,7 @@ export const HasComponentsCard = ({ variant = 'gridItem' }: Props) => {
         <div>
           No component is part of this system.{' '}
           <Link to="https://backstage.io/docs/features/software-catalog/descriptor-format#kind-component">
-            Learn how to add components.
+            (Learn how to add components.)
           </Link>
         </div>
       }

plugins/catalog/src/components/HasSubcomponentsCard/HasSubcomponentsCard.tsx

@@ -76,7 +76,7 @@ export const HasSubcomponentsCard = ({ variant = 'gridItem' }: Props) => {
         <div>
           No subcomponent is part of this component.{' '}
           <Link to="https://backstage.io/docs/features/software-catalog/descriptor-format#specsubcomponentof-optional">
-            Learn how to add subcomponents.
+            (Learn how to add subcomponents.)
           </Link>
         </div>
       }

plugins/catalog/src/components/HasSystemsCard/HasSystemsCard.tsx

@@ -73,7 +73,7 @@ export const HasSystemsCard = ({ variant = 'gridItem' }: Props) => {
         <div>
           No system is part of this domain.{' '}
           <Link to="https://backstage.io/docs/features/software-catalog/descriptor-format#kind-system">
-            Learn how to add systems.
+            (Learn how to add systems.)
           </Link>
         </div>
       }