docs: Fix link to system secret rotation (#1459)

The following link no longer exists
https://www.ory.sh/docs/hydra/advanced#system-secret-rotation

New link is here
https://www.ory.sh/docs/hydra/advanced#rotation-of-hmac-token-signing-and-database-and-cookie-encryption-keys

Signed-off-by: Shota Sawada <xiootas@gmail.com>

UPGRADE.md

@@ -243,7 +243,7 @@ are loaded (see section after next).
 Rotating system secrets was fairly cumbersome in the past and required a restart of ORY Hydra. This changed. The
 system secret is now an array where the first element is used for encryption and all elements can be used for decryption.
 
-For more information on this topic, click [here](https://www.ory.sh/docs/hydra/advanced#system-secret-rotation).
+For more information on this topic, click [here](https://www.ory.sh/docs/hydra/advanced#rotation-of-hmac-token-signing-and-database-and-cookie-encryption-keys).
 
 To make this change work, environment variable `ROTATED_SYSTEM_SECRET` has been removed and can no longer be used. Command
 `hydra migrate secret` has also been removed without replacement as it is no longer required for rotating secrets.

docs/config.yaml

@@ -359,7 +359,7 @@ oauth2:
 
 # The secrets section configures secrets used for encryption and signing of several systems. All secrets can be rotated,
 # for more information on this topic navigate to:
-# -> https://www.ory.sh/docs/hydra/advanced#system-secret-rotation
+# -> https://www.ory.sh/docs/hydra/advanced#rotation-of-hmac-token-signing-and-database-and-cookie-encryption-keys
 secrets:
   # The system secret must be at least 16 characters long. If none is provided, one will be generated. They key
   #	is used to encrypt sensitive data using AES-GCM (256 bit) and validate HMAC signatures.