Replace --project_id with --bes_instance_name (bazelbuild#1789)

The flag was renamed in bazelbuild/bazel#14507

Author: fweikert

buildkite/bazelci.py

@@ -1851,7 +1851,7 @@ def remote_caching_flags(platform, accept_cached=True):
             # Enable BES / Build Results reporting.
             "--bes_backend=buildeventservice.googleapis.com",
             "--bes_timeout=360s",
-            "--project_id=bazel-untrusted",
+            "--bes_instance_name=bazel-untrusted",
         ]
 
     platform_cache_digest = hashlib.sha256()
@@ -1963,7 +1963,7 @@ def rbe_flags(original_flags, accept_cached):
     flags += [
         "--bes_backend=buildeventservice.googleapis.com",
         "--bes_timeout=360s",
-        "--project_id=bazel-untrusted",
+        "--bes_instance_name=bazel-untrusted",
     ]
 
     if not accept_cached: