updating cert-manager version to match 2.6 notes

https://rancher.com/docs/rancher/v2.6/en/installation/install-rancher-on-k8s/
"New in v2.6.4, cert-manager versions 1.6.2 and 1.7.1 are compatible. We recommend v1.7.x because v 1.6.x will reach end-of-life on March 30, 2022."

and https://rancher.com/docs/rancher/v2.6/en/installation/install-rancher-on-k8s/
("CLICK TO EXPAND")
helm install cert-manager jetstack/cert-manager \
  --namespace cert-manager \
  --create-namespace \
  --version v1.7.1

content/rancher/v2.6/en/quick-start-guide/deployment/quickstart-manual-setup/_index.md

@@ -92,7 +92,7 @@ helm repo add rancher-latest https://releases.rancher.com/server-charts/latest
 
 kubectl create namespace cattle-system
 
-kubectl apply -f https://github.com/jetstack/cert-manager/releases/download/v1.5.1/cert-manager.crds.yaml
+kubectl apply -f https://github.com/jetstack/cert-manager/releases/download/v1.7.1/cert-manager.crds.yaml
 
 helm repo add jetstack https://charts.jetstack.io
 
@@ -101,13 +101,13 @@ helm repo update
 helm install cert-manager jetstack/cert-manager \
   --namespace cert-manager \
   --create-namespace \
-  --version v1.5.1
+  --version v1.7.1
 
 # Windows Powershell
 helm install cert-manager jetstack/cert-manager \`
   --namespace cert-manager \`
   --create-namespace \`
-  --version v1.5.1
+  --version v1.7.1
 ```
 
 The final command to install Rancher is below. The command requires a domain name that forwards traffic to the Linux machine. For the sake of simplicity in this tutorial, you can use a fake domain name to create your proof-of-concept. An example of a fake domain name would be `<IP_OF_LINUX_NODE>.sslip.io`.