Declare custom modules compatible with Drupal 9 by fiat

web/modules/custom/drutopia_case_study/drutopia_case_study.info.yml

@@ -1,7 +1,7 @@
 name: 'Drutopia Case Study'
 description: 'A Case Study highlights work done on a project.'
 type: module
-core: 8.x
+core_version_requirement: ^8 || ^9
 dependencies:
   - config_snapshot
   - drutopia_case_study
@@ -27,5 +27,4 @@ dependencies:
   - text
   - user
   - views
-version: 8.x-1.0-alpha1
 package: Drutopia