Fix capitalization: id → ID

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

roles/custom/matrix-base/defaults/main.yml

@@ -139,8 +139,8 @@ matrix_user_username: "matrix"
 matrix_user_groupname: "matrix"
 
 # By default, the playbook creates the user (`matrix_user_username`)
-# and group (`matrix_user_groupname`) with a random id.
-# To use a specific user/group id, override these variables.
+# and group (`matrix_user_groupname`) with a random ID.
+# To use a specific user/group ID, override these variables.
 matrix_user_uid: ~
 matrix_user_gid: ~