Update Stack versions in rest-api-spec updater

Author: sethmlarson

.github/workflows/update-rest-api-json.yml

@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        branch: ['main', '8.6', '8.5', '7.17']
+        branch: ['main', '8.7', '8.6', '7.17']
 
     steps:
       - uses: actions/checkout@v2