Fix another misspelled testonly
diff --git a/BUILD b/BUILD
index c73e51f..592d48e 100644
--- a/BUILD
+++ b/BUILD
@@ -11,6 +11,6 @@
         "BUILD",
         "//lib:test_deps",
     ] + glob(["*.bzl"]),
-    test_only = True,
+    testonly = True,
     visibility = ["//visibility:public"],
 )