Links with tilde ~ trip the automated tests

[Nathan Teodosio]

A snap I uploaded failed the automated test with

source-code link must have one of http|https schemes: https://code.launchpad.net/~chromium-team/chromium-browser/+git/snap-from-source/+ref/stable
                                lint-snap-v2_invalid_link

This is after I added

source-code: https://code.launchpad.net/~chromium-team/chromium-browser/+git/snap-from-source/+ref/stable

to snapcraft.yaml.

Apparently caused by the tilde in the URL.