Added missing SnippetsFilter in the HTTPRoutes in example (#3182)

Added missing SnippetsFilter in the HTTPRoutes for the snippets-filter example

Author: leonseng

Diff for: examples/snippets-filter/httproutes.yaml

@@ -13,6 +13,12 @@ spec:
         - path:
             type: PathPrefix
             value: /coffee
+      filters:
+        - type: ExtensionRef
+          extensionRef:
+            group: gateway.nginx.org
+            kind: SnippetsFilter
+            name: rate-limiting-sf
       backendRefs:
         - name: coffee
           port: 80
@@ -32,6 +38,12 @@ spec:
         - path:
             type: PathPrefix
             value: /tea
+      filters:
+        - type: ExtensionRef
+          extensionRef:
+            group: gateway.nginx.org
+            kind: SnippetsFilter
+            name: no-delay-rate-limiting-sf
       backendRefs:
         - name: tea
           port: 80