Removed trailing slash to fix linter error
Removed trailing slash to fix linter error

The `https://atom.io` link included a trailing slash which caused the linter to error. Although unrelated to the open PR, I'm fixing this to address [linter issues](https://travis-ci.org/carlosperate/awesome-microbit/builds/152389153).
carlosperate/awesome-microbit,carlosperate/awesome-microbit