Update buildkite plugin shellcheck to v1.2.0

Author: renovate-bot

.buildkite/pipeline.yml

@@ -6,7 +6,7 @@ steps:
 
   - label: ":bash: Shellcheck"
     plugins:
-      shellcheck#v1.1.2:
+      shellcheck#v1.2.0:
         files: hooks/**
 
   - label: ":bash: Tests"