Merge pull request #27114 from mengjiao-liu/update-signerName-desc

update certificate-signing-requests Signer description

Author: k8s-ci-robot

content/en/docs/reference/access-authn-authz/certificate-signing-requests.md

@@ -60,7 +60,7 @@ state for some duration:
 
 ## Signers
 
-All signers should provide information about how they work so that clients can predict what will happen to their CSRs.
+Custom signerNames can also be specified. All signers should provide information about how they work so that clients can predict what will happen to their CSRs.
 This includes:
 
 1. **Trust distribution**: how trust (CA bundles) are distributed.