updated release-version mapping for MCE 2.7

Signed-off-by: dislbenn <[email protected]>

Author: dislbenn

.github/release-version-mapping.yaml

@@ -4,7 +4,7 @@
 
 release_mappings:
   backplane-2.6: "2.6.9"
-  backplane-2.7: "2.7.7"  
+  backplane-2.7: "2.7.6"  
   backplane-2.8: "2.8.3"
   backplane-2.9: "2.9.1"
   backplane-2.10: "2.10.0"