_sandboxbuildboxrun.py: Drop --use-localcas

This option has been deprecated in BuildBox upstream for a year and will
be removed.
diff --git a/.github/compose/ci.buildgrid.yml b/.github/compose/ci.buildgrid.yml
index 211c320..0b37e9f 100644
--- a/.github/compose/ci.buildgrid.yml
+++ b/.github/compose/ci.buildgrid.yml
@@ -38,7 +38,7 @@
   bot:
     image: registry.gitlab.com/buildgrid/buildgrid.hub.docker.com/buildbox:nightly
     command: [
-      "sh", "-c", "sleep 15 && ( buildbox-casd --cas-remote=http://controller:50051 /var/lib/buildgrid/cache & buildbox-worker --request-timeout=30 --bots-remote=http://controller:50051 --cas-remote=unix:/var/lib/buildgrid/cache/casd.sock --buildbox-run=buildbox-run-bubblewrap --runner-arg=--use-localcas --platform OSFamily=linux --platform ISA=x86-64 --verbose )"]
+      "sh", "-c", "sleep 15 && ( buildbox-casd --cas-remote=http://controller:50051 /var/lib/buildgrid/cache & buildbox-worker --request-timeout=30 --bots-remote=http://controller:50051 --cas-remote=unix:/var/lib/buildgrid/cache/casd.sock --buildbox-run=buildbox-run-bubblewrap --platform OSFamily=linux --platform ISA=x86-64 --verbose )"]
     privileged: true
     volumes:
       - type: volume
diff --git a/src/buildstream/sandbox/_sandboxbuildboxrun.py b/src/buildstream/sandbox/_sandboxbuildboxrun.py
index e489c9b..9880875 100644
--- a/src/buildstream/sandbox/_sandboxbuildboxrun.py
+++ b/src/buildstream/sandbox/_sandboxbuildboxrun.py
@@ -94,7 +94,6 @@
 
             buildbox_command = [
                 utils.get_host_tool("buildbox-run"),
-                "--use-localcas",
                 "--remote={}".format(casd_process_manager._connection_string),
                 "--action={}".format(action_file.name),
                 "--action-result={}".format(result_file.name),