Update build.yaml

Author: calandradas

.github/workflows/build.yaml

@@ -27,5 +27,5 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.R8000_ACT }}
         with:
-          tag_name: 'Kminder-Mindmap-Joplin-Plugin-$(date +"%Y.%m.%d-%H%M")'
+          tag_name: 'Kminder-Mindmap-Joplin-Plugin-0.8.7'
           files: ./publish/*