[docs] Simplify the /examples

[oliviertassinari]

Follow-up on #14767 as released.

[mui-pr-bot]

Details of bundle changes.

Comparing: 3a5d2e5...528298d

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	0.00%	0.00%	362,777	362,777	92,213	92,213
@material-ui/core/Paper	0.00%	0.00%	68,878	68,878	20,170	20,170
@material-ui/core/Paper.esm	0.00%	0.00%	63,340	63,340	19,272	19,272
@material-ui/core/Popper	0.00%	0.00%	30,460	30,460	10,573	10,573
@material-ui/core/styles/createMuiTheme	0.00%	0.00%	17,284	17,284	5,700	5,700
@material-ui/core/useMediaQuery	0.00%	0.00%	2,471	2,471	1,035	1,035
@material-ui/lab	0.00%	0.00%	170,747	170,747	50,065	50,065
@material-ui/styles	0.00%	0.00%	57,220	57,220	16,273	16,273
@material-ui/system	0.00%	0.00%	17,041	17,041	4,493	4,493
Button	0.00%	0.00%	91,152	91,152	26,939	26,939
Modal	0.00%	0.00%	90,261	90,261	26,724	26,724
colorManipulator	0.00%	0.00%	3,232	3,232	1,298	1,298
docs.landing	0.00%	0.00%	51,908	51,908	11,302	11,302
docs.main	0.00%	-0.00%	647,805	647,808	201,560	201,557
packages/material-ui/build/umd/material-ui.production.min.js	0.00%	0.00%	311,179	311,179	85,197	85,197

Generated by 🚫 dangerJS against 528298d