access_control.md: edit GRANT examples

Summary

• fix(access_control.md): typos in GRANT example
• access_control.md: sync examples with grant.svg

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• Cherry-pick to: 24.4
• Staging:
  • https://docs.binary.picodata.io/picodata/asabirov_fix_grant_examples/tutorial/access_control/
  • https://docs.binary.picodata.io/picodata/asabirov_fix_grant_examples/reference/sql/grant/