pw_env_setup: Get cas from cipd

Also remove isolated from CIPD. CAS-RBE is replacing isolated.

Change-Id: Idb927f4f2ab80c2d3fa6322ca68a433529ca989a
Bug: 380
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/44680
Reviewed-by: Ewout van Bekkum <ewout@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
diff --git a/pw_env_setup/py/pw_env_setup/cipd_setup/luci.json b/pw_env_setup/py/pw_env_setup/cipd_setup/luci.json
index 1cb2bf7..240a571 100644
--- a/pw_env_setup/py/pw_env_setup/cipd_setup/luci.json
+++ b/pw_env_setup/py/pw_env_setup/cipd_setup/luci.json
@@ -24,7 +24,7 @@
         ]
     },
     {
-        "path": "infra/tools/luci/isolated/${platform}",
+        "path": "infra/tools/luci/cas/${platform}",
         "tags": [
             "latest"
         ]