ci: adjust trigger conditions for cesium-dashboard workflow (#10)

These conditions make more sense when using release-please

.github/workflows/cesium-dashboard-image.yml

@@ -1,15 +1,12 @@
 name: cesium-dasbhoard-image
 
 on:
-  schedule:
-    - cron: '17 2 * * *'
   push:
-    branches: [ "main" ]
+    branches:
+      - 'main'
     # Publish semver tags as releases.
-    tags: [ 'v*.*.*' ]
-  pull_request:
-    branches: [ "main" ]
-
+    tags:
+      - 'v*.*.*'
 env:
   REGISTRY: ghcr.io
   IMAGE_NAME: forumviriumhelsinki/cesium-dashboard