Update dead link in nginx/HTTPS section

[DanielMSchmidt]

Hi there,

First of all thanks for maintaining this awesome project 👍
I found a dead link in the readme, I hope I fixed.

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[k8s-reviewable]

This change is 

[coveralls]

Coverage remained the same at 44.687% when pulling a910661 on DanielMSchmidt:patch-1 into f1598b3 on kubernetes:master.

[aledbf]

/lgtm

[aledbf]

@DanielMSchmidt thanks!