docs: update link to configuring http proxy for dockerd

[dvdksn]

Signed-off-by: David Karlsson david.karlsson@docker.com

- What I did

Updated doc links for how to configure HTTP/HTTPS proxy for the daemon

See docker/docs#13786

- How I did it

- How to verify it

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

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[thaJeztah]

let me "request changes" for now while we decide which approach to take; see docker/docs#13786 (comment)