master.chromeos.release: Mark readonly.

Mark the master.chromeos.release bucket read only, since the waterfall
is going away. This should allow us to keep reading information about
existing builds, while confirming that we don't create new ones.

BUG=chromium:908918
TEST=None

Change-Id: I61871c2f3d0adb0a9ef3b16741b53bfb080da073
Reviewed-on: https://chromium-review.googlesource.com/c/1351640
Reviewed-by: Mike Nichols <mikenichols@chromium.org>
Commit-Queue: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
diff --git a/cr-buildbucket.cfg b/cr-buildbucket.cfg
index 69f7e96..c2b63c2 100644
--- a/cr-buildbucket.cfg
+++ b/cr-buildbucket.cfg
@@ -12,22 +12,6 @@
   }
 }
 
-acl_sets {
-  name: "waterfall"
-  acls {
-    role: READER
-    group: "project-chromeos-buildbucket-readers"
-  }
-  acls {
-    role: WRITER
-    group: "project-chromeos-buildbucket-writers"
-  }
-  acls {
-    role: SCHEDULER
-    group: "project-chromeos-buildbucket-schedulers"
-  }
-}
-
 # Please keep this list sorted by bucket name.
 
 buckets {
@@ -37,7 +21,7 @@
 
 buckets {
   name: "master.chromeos_release"
-  acl_sets: "waterfall"
+  acl_sets: "readonly"
 }
 
 buckets {