Docs: DR replication API updates (#20373)

* Docs: DR replication API updates

- Add clarification for secondary_public_key parameter
- Update section header

* During activation

website/content/api-docs/system/replication/replication-dr.mdx

@@ -178,7 +178,8 @@ identifier can later be used to revoke a DR secondary's access.
 
 - `secondary_public_key` `(string: "")` – Specifies the secondary's generated
   public key, if using encryption rather than response wrapping to protect the
-  secondary credentials. (Vault 1.3+)
+  secondary credentials. (Vault 1.3+). Use this to avoid making an API call to
+  the primary during secondary activation.
 
 ### Sample Payload
 
@@ -249,11 +250,11 @@ $ curl \
     http://127.0.0.1:8200/v1/sys/replication/dr/primary/revoke-secondary
 ```
 
-## Fetch DR Secondary Public Key
+## Generate DR Secondary Public Key
 
 (Vault 1.3+)
 
-This endpoint allows fetching a public key that is used to encrypt the returned
+This endpoint allows generating a public key that is used to encrypt the returned
 credential information (instead of using a response wrapped token). This avoids
 needing to make an API call to the primary during activation.