This edit is bad and was correctly rejected.
The edit does not add any value to the post or improve it in any way. At best, it is "too minor". At worst, it is actually detrimental, as it replaces what was a validly formatted link with something that is not.
If one was going to replace the URL with a "placeholder" (e.g. because it revealed proprietary information or was unnecessary spammy), she should use the canonical example URL: http://www.example.com/.
But I would still consider that to be "too minor", unless it was coupled with some other substantial edits.