The installation instructions on the website vysor.io cause a vysor.list file to be added in your /etc/apt/sources.list.d directory. The list file contains a link to the vysor repository. Although you have removed the package itself, the .list file is still there and will be consulted by apt every time you look for updates. Of course, no relevant update is found.
The way to avoid the .list file being read is to remove it. Another way would be to rename it to something like vysor.link.backup in case you change your mind, as only files with the .list extension are read.
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