Non-HTTPS links on website

[gravityFlower]

Bug Report

• [x] Yes, I reviewed the contribution guidelines.
• [x] Yes, more specifically, I reviewed the guidelines on how to write clear bug reports.

Describe the current, buggy behavior Documentation site for at least one foreign language partially broken. Mixed content browser warning.

Describe how other contributors can replicate this bug

• visit https://wp-cli.org
• change language to Deutsch
• click on doc link after wp transient delete-all or
• follow link Quick Start guide or
• follow link komplette Liste an Befehlen

Describe what you expect as the correct outcome

Expected behaviour:

• browser shouldn't show warning of insecure site due to mixed content
• browser should redirect to correct github page instead of a github 404

Let us know what environment you are running this on Browser used: Firefox 72.0.2 (64-Bit) Windows 10 x64

Provide a possible solution

• fix links to redirect to correct site
• fix https mixed content issue
• check links in other languages too (maybe scrape and check for non 200/301/302 http status codes?)

[schlessera]

It seems that the German translation for the page hasn't been kept up-to-date for quite a while. I'll take a stab at translating it myself, unless someone volunteers to take care of it.