Header & HeaderTabs components: make className prop optional

Signed-off-by: Raghunandan <soapraj@gmail.com>

packages/core-components/src/layout/Header/Header.tsx

@@ -113,7 +113,7 @@ type Props = {
   tooltip?: string;
   type?: string;
   typeLink?: string;
-  className: string | '';
+  className?: string | '';
 };
 
 type TypeFragmentProps = {

packages/core-components/src/layout/HeaderTabs/HeaderTabs.tsx

@@ -67,7 +67,7 @@ type HeaderTabsProps = {
   tabs: Tab[];
   onChange?: (index: number) => void;
   selectedIndex?: number;
-  className: string | '';
+  className?: string | '';
 };
 
 /**