drop deprecated `autotick` attribute of cartesian axes in v3

[archmoj]

plotly.js/src/plots/cartesian/layout_attributes.js

Lines 1243 to 1252 in 206d117

	_deprecated: {
	autotick: {
	valType: 'boolean',
	editType: 'ticks',
	description: [
	'Obsolete.',
	'Set `tickmode` to *auto* for old `autotick` *true* behavior.',
	'Set `tickmode` to *linear* for `autotick` *false*.'
	].join(' ')
	},