Align `SSH_AUTHORIZED_KEYS_BACKUP` var with the value in `app.ini` (#13212)

* Align `SSH_AUTHORIZED_KEYS_BACKUP` var with the value in `app.ini`

* Also fix the cheat sheet and move it to below - SSH_CREATE_AUTHORIZED_KEYS_FILE

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Andrew Thornton <art27@cantab.net>

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -251,6 +251,7 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 - `SSH_LISTEN_PORT`: **%(SSH\_PORT)s**: Port for the built-in SSH server.
 - `SSH_ROOT_PATH`: **~/.ssh**: Root path of SSH directory. 
 - `SSH_CREATE_AUTHORIZED_KEYS_FILE`: **true**: Gitea will create a authorized_keys file by default when it is not using the internal ssh server. If you intend to use the AuthorizedKeysCommand functionality then you should turn this off.
+- `SSH_AUTHORIZED_KEYS_BACKUP`: **true**: Enable SSH Authorized Key Backup when rewriting all keys, default is true.
 - `SSH_TRUSTED_USER_CA_KEYS`: **\<empty\>**: Specifies the public keys of certificate authorities that are trusted to sign user certificates for authentication. Multiple keys should be comma separated. E.g.`ssh-<algorithm> <key>` or `ssh-<algorithm> <key1>, ssh-<algorithm> <key2>`. For more information see `TrustedUserCAKeys` in the sshd config man pages. When empty no file will be created and `SSH_AUTHORIZED_PRINCIPALS_ALLOW` will default to `off`.
 - `SSH_TRUSTED_USER_CA_KEYS_FILENAME`: **`RUN_USER`/.ssh/gitea-trusted-user-ca-keys.pem**: Absolute path of the `TrustedUserCaKeys` file gitea will manage. If you're running your own ssh server and you want to use the gitea managed file you'll also need to modify your sshd_config to point to this file. The official docker image will automatically work without further configuration.
 - `SSH_AUTHORIZED_PRINCIPALS_ALLOW`: **off** or **username, email**: \[off, username, email, anything\]: Specify the principals values that users are allowed to use as principal. When set to `anything` no checks are done on the principal string. When set to `off` authorized principal are not allowed to be set.
@@ -261,7 +262,6 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 - `SSH_SERVER_MACS`: **hmac-sha2-256-etm@openssh.com, hmac-sha2-256, hmac-sha1, hmac-sha1-96**: For the built-in SSH server, choose the MACs to support for SSH connections, for system SSH this setting has no effect
 - `SSH_KEY_TEST_PATH`: **/tmp**: Directory to create temporary files in when testing public keys using ssh-keygen, default is the system temporary directory.
 - `SSH_KEYGEN_PATH`: **ssh-keygen**: Path to ssh-keygen, default is 'ssh-keygen' which means the shell is responsible for finding out which one to call.
-- `SSH_BACKUP_AUTHORIZED_KEYS`: **true**: Enable SSH Authorized Key Backup when rewriting all keys, default is true.
 - `SSH_EXPOSE_ANONYMOUS`: **false**: Enable exposure of SSH clone URL to anonymous visitors, default is false.
 - `MINIMUM_KEY_SIZE_CHECK`: **true**: Indicate whether to check minimum key size with corresponding type.
 

docs/content/doc/installation/with-docker.en-us.md

@@ -371,7 +371,7 @@ config:
 
 ```
 [ssh]
-SSH_BACKUP_AUTHORIZED_KEYS=false
+SSH_AUTHORIZED_KEYS_BACKUP=false
 ```
 
 - mount your `.ssh` directory directly into the container i.e. add the