Update enabling-automatic-tls-certificate-provisioning.md (#5933)

ConfigMap values can only be of type String

Author: hubwoop

docs/serving/encryption/enabling-automatic-tls-certificate-provisioning.md

@@ -174,7 +174,7 @@ For example, you can use the following configurations:
 You can also configure the selector to opt-out when a specific label is on the namespace:
 
 ```yaml
-namespace-wildcard-cert-selector:
+namespace-wildcard-cert-selector: |-
   matchExpressions:
   - key: "networking.knative.dev/disableWildcardCert"
     operator: "NotIn"
@@ -185,7 +185,7 @@ This selects all namespaces where the label value is not in the set `"true"`.
 Or use existing kubernetes labels to select namespaces based on their name:
 
 ```yaml
-namespace-wildcard-cert-selector:
+namespace-wildcard-cert-selector: |-
   matchExpressions:
     - key: "kubernetes.io/metadata.name"
       operator: "In"