chore: disable nightly acceptance tests

The time-cost of cleaning up after flakes, and investing in making
flakes less frequent, isn't worth the benefit we get from these, given
that we rarely make changes to this repo anymore.

We can run acceptance tests manually, against branches, by passing
ACC_TESTS=1 in CircleCI if we feel the need, to test specific changes.

.circleci/config.yml

@@ -226,30 +226,6 @@ jobs:
                 project: ${CIRCLE_PROJECT_REPONAME}
                 organization: cloud-cloud
 workflows:
-  nightly:
-    jobs:
-      - test_acc:
-          name: "Acceptance tests: << matrix.pattern >>"
-          matrix:
-            parameters:
-              pattern:
-                - TestAcc_Aws
-                - TestAcc_Google
-                - TestAcc_Azure_
-                - TestAcc_StateReader_
-
-                # Disable this rather than create a new test org
-                # - TestAcc_Github_
-          context:
-            - driftctl-acc
-            - snyk-bot-slack
-    triggers:
-      - schedule:
-          cron: "0 3 * * *"
-          filters:
-            branches:
-              only:
-                - main
   manual-acc-tests:
     when:
       equal: ['1', << pipeline.parameters.ACC_TESTS >>]