It looks like this is because you are using single quotes around the path.
If you have a variable within single quotes ($envCommonDesktop in your case), it is not expanded, meaning the command is trying to remove a file named $envCommonDesktop\file1.txt or $envCommonDesktop\file2.txt which neither exists.
IMHO you should change this to use double quotes, so the variable is correctly expanded, plus it is wise to wrap the variable within a $() so that if the path contains spaces it is determined correctly, this would mean your lines should read::
Remove-File -Path "$($envCommonDesktop)\file1.txt"
Remove-File -Path "$($envCommonDesktop)\file2.txt"