[charts] Use `<circle />` instead of `<path />` for line marks by default

[alexfauquette]

Still need to add tests, and verify I did not impacted badly perfs with the new shape support

[mui-bot]

Deploy preview: https://deploy-preview-15220--material-ui-x.netlify.app/

Updated pages:

• docs/data/charts/line-demo/line-demo.md
• docs/data/migration/migration-charts-v7/migration-charts-v7.md

Generated by :no_entry_sign: dangerJS against baf0c050fa30ac344a97f59cf9ecfe02204a0970

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #15220 will not alter performance

_{Comparing alexfauquette:perf-line (baf0c05) with master (08b9c66)}

Summary

✅ 6 untouched benchmarks

[github-actions[bot]]

This pull request has conflicts, please resolve those before we can evaluate the pull request.