docs: Update group membership fields to match application. (#28175)

Several fields in the "Verify group membership in LDAP" docs were
confusingly titled when compared to the actual fields in the
application, this change rectifies that by matching the docs to the
fields already present in gitea.

Signed-off-by: David Hulick <dave.hulick@gmail.com>

docs/content/usage/authentication.en-us.md

@@ -145,25 +145,25 @@ Adds the following fields:
 
 Uses the following fields:
 
-- Group Search Base (optional)
+- Group Search Base DN (optional)
 
   - The LDAP DN used for groups.
   - Example: `ou=group,dc=mydomain,dc=com`
 
-- Group Name Filter (optional)
-
-  - An LDAP filter declaring how to find valid groups in the above DN.
-  - Example: `(|(cn=gitea_users)(cn=admins))`
+- Group Attribute Containing List Of Users (optional)
+  - The attribute of the group object that lists/contains the group members.
+  - Example: `memberUid` or `member`
 
-- User Attribute in Group (optional)
+- User Attribute Listed in Group (optional)
 
   - The user attribute that is used to reference a user in the group object.
   - Example: `uid` if the group objects contains a `member: bender` and the user object contains a `uid: bender`.
   - Example: `dn` if the group object contains a `member: uid=bender,ou=users,dc=planetexpress,dc=com`.
 
-- Group Attribute for User (optional)
-  - The attribute of the group object that lists/contains the group members.
-  - Example: `memberUid` or `member`
+- Verify group membership in LDAP (optional)
+
+  - An LDAP filter declaring how to find valid groups in the above DN.
+  - Example: `(|(cn=gitea_users)(cn=admins))`
 
 ## PAM (Pluggable Authentication Module)