Add comment explaining venv cleanup find command

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

containers/grafana-sidecar/container.py

@@ -32,6 +32,7 @@ async def build(src: dagger.Directory) -> dagger.Container:
         .with_file("/app/pyproject.toml", source.file("pyproject.toml"))
         .with_directory("/app/src", source.directory("src"))
         .with_exec([".venv/bin/pip", "install", "--no-cache-dir", "."])
+        # Strip test dirs and bytecode from venv to shrink the image
         .with_exec(
             [
                 "sh",