Set the page size to 50

To make it extra unlikely that the guide one's looking for is not in the
first page.

Compromise to address #40 (comment)

src/main/java/io/quarkus/search/app/SearchService.java

@@ -25,7 +25,7 @@
 @Path("/")
 public class SearchService {
 
-    private static final Integer PAGE_SIZE = 20;
+    private static final Integer PAGE_SIZE = 50;
 
     @Inject
     SearchSession session;