Improve flaky snippet_index_page_spec test

Wait for snippet statistics to be created and computed
See https://gitlab.com/gitlab-org/gitlab/-/issues/338313

qa/qa/page/dashboard/snippet/index.rb

@@ -35,8 +35,10 @@ module QA
           end
 
           def has_number_of_files?(snippet_title, number)
+            retry_until(max_attempts: 5, reload: true, sleep_interval: 1) do # snippet statistics computation can take a few moments
               within_element(:snippet_link, snippet_title: snippet_title) do
-              has_element?(:snippet_file_count_content, snippet_files: number)
+                has_element?(:snippet_file_count_content, snippet_files: number, wait: 5)
+              end
             end
           end
         end