Don't render header divider on homepage cards if no title was specified.

Some homepage cards would like to define their own header
for example, so that a title can be set dynamically.

Removing the divider with the divider prop provides a way to put
everything in the content area without an extraneous divider above.

The divider is usually not easily visible using the default theme,
however customized themes that may use a larger border-radius this
divider becomes visible and distracting.

Signed-off-by: Adam Kunicki <kunickiaj@gmail.com>

.changeset/late-hairs-kneel.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-home-react': patch
+---
+
+Don't render header divider on homepage cards if no title was specified.

plugins/home-react/src/extensions.tsx

@@ -47,7 +47,9 @@ export type RendererProps = { title?: string } & ComponentParts;
 /**
  * @public
  */
-export type CardExtensionProps<T> = ComponentRenderer & { title?: string } & T;
+export type CardExtensionProps<T> = ComponentRenderer & {
+  title?: string;
+} & T;
 
 /**
  * @public
@@ -150,7 +152,7 @@ function CardExtension<T>(props: CardExtensionComponentProps<T>) {
   }
 
   const cardProps = {
-    ...(title && { title }),
+    ...(title && { title, divider: !!title }),
     ...(Settings && !isCustomizable
       ? {
           action: (