Fix typo in SDK maintainer label (remove a plural). (project-chip#40198)

Co-authored-by: Andrei Litvin <[email protected]>

Author: andy31415

.pullapprove.yml

@@ -51,7 +51,7 @@ overrides:
   ############################################################
   #  Approved by matter-sdk-maintainers
   ############################################################
-  - if: "'sdk-maintainers-approved' in labels and len(groups.approved.include('sdk-maintainers')) >= 1"
+  - if: "'sdk-maintainer-approved' in labels and len(groups.approved.include('sdk-maintainers')) >= 1"
     status: success
     explanation: "Approved by SDK maintainer and label is set."