fix supplements reference

Co-authored-by: Kurt Garloff <kurt@garloff.de>
Signed-off-by: Marvin Frommhold <depressiveRobot@users.noreply.github.com>

Author: depressiveRobot

Standards/scs-0007-w1-certification-integrators-implementation-notes.md

@@ -4,7 +4,7 @@ type: Supplement
 track: Global
 status: Draft
 supplements:
-  - scs-0007-v1-certification-integrators.ms
+  - scs-0007-v1-certification-integrators.md
 ---
 
 ## Introduction