[docs] Fix bash comments

[oliviertassinari]

It's wrong: https://phoenixnap.com/kb/bash-comment

Before https://next.mui.com/x/migration/migration-pickers-v7/#run-codemods

After https://deploy-preview-15571--material-ui-x.netlify.app/x/migration/migration-pickers-v7/#run-codemods

[mui-bot]

Deploy preview: https://deploy-preview-15571--material-ui-x.netlify.app/

Updated pages:

• docs/data/migration/migration-charts-v7/migration-charts-v7.md
• docs/data/migration/migration-data-grid-v5/migration-data-grid-v5.md
• docs/data/migration/migration-data-grid-v6/migration-data-grid-v6.md
• docs/data/migration/migration-pickers-v5/migration-pickers-v5.md
• docs/data/migration/migration-pickers-v6/migration-pickers-v6.md

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