Recognize trusted iMac CI workers (#2015)

diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index a47fa16..64fe68e 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -607,7 +607,7 @@
 MAX_TASK_NUMBER = 80
 
 LAB_AGENT_PATTERNS = [
-    re.compile(r"^bk-imacpro-\d+$"),
+    re.compile(r"^bk-(trusted-)?imacpro-\d+$"),
     re.compile(r"^bk-(trusted|testing)-macpro-\d+$"),
     re.compile(r"^bk-(trusted-)?macstudio-\d+$"),
 ]