(docs) Fixed broken link to "setuid sandbox"

[clayzermk1]

Minor documentation fix.

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[clayzermk1]

@googlebot I signed it!

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[jackfranklin]

Thanks for this!

I noticed at the top of the new docs it says:

IMPORTANT NOTE: The Linux SUID sandbox is almost but not completely removed. See
https://bugs.chromium.org/p/chromium/issues/detail?id=598454 This page is mostly out-of-date.

I therefore wonder if we should just remove this stuff from our docs. @mathiasbynens wdyt?