chore(deps): update buildkite/plugin-tester docker tag to v4.2.0

Author: felix-renovate[bot]

docker-compose.yml

@@ -16,6 +16,6 @@ services:
       - --id=planetscale/telemetry
 
   tests:
-    image: buildkite/plugin-tester:v4.1.1@sha256:581f73aca88169912e23809f323437cced3cf22c28794bd7f96fbdf1c2caa5ab
+    image: buildkite/plugin-tester:v4.2.0@sha256:21067012f59af6b8316cceb95850e89a542b50338c72d209a68bbebb33aff8c3
     volumes:
       - ".:/plugin:ro"