CONTRIBUTING.md: point folks towards update_tests.sh
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index d574007..b29dca8 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -15,9 +15,4 @@
 
 A few tests record/replay calls to LLMs. As necessary (e.g.,
 if changing the system prompt or tool definitions), rebuild the
-test data with:
-
-```
-go test ./dockerimg -httprecord ".*" -rewritewant
-go test ./loop -httprecord .*agent_.*
-```
+test data by running update_tests.sh in the relevant directory.