Minor fix to find the pinned revision

Author: rafabene

documentation/modules/ROOT/pages/02-basic-fundas.adoc

@@ -257,7 +257,7 @@ Let us redeploy the greeter service by pinning it to the first revision that was
 [#run-pinned-revision]
 [source,bash,subs="+macros,+attributes"]
 ----
-PIN_REVISION=`kubectl get rev -l serving.knative.dev/service=greeter -l serving.knative.dev/configurationGeneration=1 | awk 'NR==2{print $1}'` && \
+PIN_REVISION=`kubectl get rev -n knativetutorial -l serving.knative.dev/service=greeter -l serving.knative.dev/configurationGeneration=1 | awk 'NR==2{print $1}'` && \
 cat service-pinned.yaml | yq w - "spec.release.revisions[+]" $PIN_REVISION | kubectl -n {tutorial-namespace} apply -f -
 ----
 copyToClipboard::run-pinned-revision[]