Clarify what openshiftci-config.sh is used for

Author: rm3l

scripts/openshiftci-config.sh

@@ -1 +1,4 @@
+# This is used in openshiftci-presubmit-all-tests.sh, used by Interop tests.
+# Since these interop tests are managed by a different team, we intentionally want to use a stable Devfile registry.
+# But our own internal tests make use of the staging Devfile registry.
 export DEVFILE_REGISTRY=https://devfile-registry-ci-devfile-registry.odo-test-kubernete-449701-49529fc6e6a4a9fe7ebba9a3db5b55c4-0000.eu-de.containers.appdomain.cloud/