[charts] Remove require condition from package.json exports

[Janpot]

At the moment we don't have a working commonjs export for @mui/x-charts. We're using this alpha package to test the waters in the community about support for ESM modules. As such it makes sense to remove the non-working require condition, and supply a default condition as a fallback. Alternatively we could opt for removing the import condition altogether and just keeping default.

Closes #10257
Closes #10195

• https://deploy-preview-10272--material-ui-x.netlify.app/x/react-charts/bars/
• https://codesandbox.io/s/jsttrw?file=/Demo.tsx

[mui-bot]

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These are the results for the performance tests:

Test case	Unit	Min	Max	Median	Mean	σ
Filter 100k rows	ms	-217.3	24.8	-217.3	-85	87.995
Sort 100k rows	ms	577.4	1,483.1	1,419	1,173.44	337.393
Select 100k rows	ms	604.1	899.4	770.2	748.52	98.5
Deselect 100k rows	ms	169.5	310.3	174.6	206.12	53.357

Generated by 🚫 dangerJS against 0f3dde6

[LukasTy]

LGTM! 💯
Thank you for taking the time to investigate the problem. 🙏