[docs] Fix Drawer demos accessibility

[tiagodreis]

• I have followed (at least) the PR section of the contributing guide.

Closes #14718

[mui-pr-bot]

Details of bundle changes.

Comparing: 7996285...fd83c21

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	0.00%	0.00%	371,600	371,600	91,877	91,877
@material-ui/core/Paper	0.00%	0.00%	76,930	76,930	19,372	19,372
@material-ui/core/Paper.esm	0.00%	0.00%	71,601	71,601	18,779	18,779
@material-ui/core/Popper	0.00%	0.00%	30,462	30,462	10,582	10,582
@material-ui/core/styles/createMuiTheme	0.00%	0.00%	17,286	17,286	5,717	5,717
@material-ui/core/useMediaQuery	0.00%	0.00%	2,486	2,486	1,048	1,048
@material-ui/lab	0.00%	0.00%	184,505	184,505	50,732	50,732
@material-ui/styles	0.00%	0.00%	57,720	57,720	16,273	16,273
@material-ui/system	0.00%	0.00%	17,062	17,062	4,487	4,487
Button	0.00%	0.00%	99,633	99,633	26,634	26,634
Modal	0.00%	0.00%	98,713	98,713	26,171	26,171
colorManipulator	0.00%	0.00%	3,232	3,232	1,296	1,296
docs.landing	0.00%	-0.01%	51,773	51,773	11,245	11,244
docs.main	0.00%	0.00%	678,825	678,825	206,233	206,233
packages/material-ui/build/umd/material-ui.production.min.js	0.00%	0.00%	322,256	322,256	85,048	85,048

Generated by 🚫 dangerJS against fd83c21

[oliviertassinari]

@tiagodreis It's a great first pull request on Material-UI 👌🏻. Thank you for working on it!

[tiagodreis]

Thank you, @oliviertassinari ! :)