Some images have alt text displayed in lesson

[martinosorb]

What is the problem?

{alt=‘Clicking the “Copy to Clipboard” button on GitHub to obtain the repository’s URL’}
is shown as part of the text. There are several places where this is the case. I believe it was introduced in a recent PR. Will look into this asap.

Location of problem (optional)

e.g. https://swcarpentry.github.io/git-novice/aio.html#connect-local-to-remote-repository