Remove duping secondaryColor button on about:styles

[luixxiul]

Test plan

#9560 (comment)

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Describe the issue you encountered: Remove a duping secondaryColor button on about:styles

browser-laptop/js/about/styles.js

Lines 260 to 263 in 3dfc598

	<BrowserButton secondaryColor l10nId='secondaryColor' onClick={this.onRemoveBookmark} />
	<Pre><Code>
	&lt;BrowserButton secondaryColor l10nId='secondaryColor' onClick={'{this.onRemoveBookmark}'} />
	</Code></Pre>

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