clean schema file first (#287)

Author: kddejong

.github/workflows/template-schema-updater.yaml

@@ -22,6 +22,7 @@ jobs:
           cd aws-cloudformation-template-schema
           poetry install
           poetry run cfn-template-schema generate --output-folder specs --type language-server
+          rm -Rf ../server/schema/*
           mv specs/* ../server/schema/
           cd ..
           rm -rf aws-cloudformation-template-schema