wiki: load embedded images over https to avoid mixed content

[triuzzi]

Problem

Mobile.md and GoArm.md embed screenshots via http:// URLs. Because https://go.dev is served over HTTPS, these are mixed content: browsers either block the request or must silently upgrade it, so the images can fail to display.

Affected references:

• Mobile.md — 4× http://i.imgur.com/…
• GoArm.md — 1× http://farm8.staticflickr.com/…

Fix

Switch the five references to https://. Each host already serves the identical file over HTTPS (verified: imgur → 200 image/png, flickr → 200 image/jpeg), so this is a scheme-only change with no other content edits.

Companion to #102, which fixes the /blob/ module-diagram images. Together they make every embedded image on the wiki load reliably on the HTTPS site.

[gopherbot]

This PR (HEAD: 1e25e5c) has been imported to Gerrit for code review.

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[gopherbot]

Message from Sean Liao:

Patch Set 1:

(1 comment)

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