Update web-ui-dashboard.md

[Rajakavitha1]

Updated the URL as mentioned in: https://github.com/kubernetes/dashboard/wiki/Accessing-Dashboard---1.7.X-and-above as a fix for #8119

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For 1.11 Features: set Milestone to 1.11 and Base Branch to release-1.11
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[Rajakavitha1]

/assign @bradtopol

[chenopis]

/lgtm
/approve

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