clarify specification of audit log types (GoogleCloudPlatform#3136)

This change is intended to avoid the confusion outlined in
hashicorp/terraform-provider-google#5446,
which I also ran into. Having multiple audit logs in the example should
make it readily apparent how the resource is intended to be used.

third_party/terraform/website/docs/r/google_project_iam.html.markdown

@@ -138,6 +138,9 @@ resource "google_project_iam_member" "project" {
 resource "google_project_iam_audit_config" "project" {
   project = "your-project-id"
   service = "allServices"
+  audit_log_config {
+    log_type = "ADMIN_READ"
+  }
   audit_log_config {
     log_type = "DATA_READ"
     exempted_members = [