Update quickstart.mdx (#742)

Fixed the indentation on yaml

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Author: batchunag

docs/batch-changes/quickstart.mdx

@@ -55,7 +55,7 @@ on:
 # In each repository, run this command. Each repository's resulting diff is captured.
 steps:
  - run: IFS=$'\n'; echo Hello World | tee -a $(find -name README)
- container: alpine:3
+   container: alpine:3
 
 # Describe the changeset (e.g., GitHub pull request) you want for each repository.
 changesetTemplate: