[accessibility-2950560}:[Programmatic Access-Try Cosmos DB-Welcome! What is Cosmos DB?]: 'Welcome! What is Cosmos DB?' is not defined programmatically as heading. (#1882)

Co-authored-by: Satyapriya Bai <v-satybai@microsoft.com>

src/Explorer/Quickstart/QuickstartCarousel.tsx

@@ -24,7 +24,9 @@ export const QuickstartCarousel: React.FC<QuickstartCarouselProps> = ({
     >
       <Stack>
         <Stack horizontal horizontalAlign="space-between" style={{ padding: 16 }}>
-          <Text variant="xLarge">{getHeaderText(page)}</Text>
+          <Text role="heading" aria-level={1} variant="xLarge">
+            {getHeaderText(page)}
+          </Text>
           <IconButton iconProps={{ iconName: "Cancel" }} onClick={() => setPage(4)} ariaLabel="Close" />
         </Stack>
         {getContent(page)}