Deprecate `donjayamanne.python-environment-manager`

[amvanbaren]

source: https://open-vsx.org/extension/donjayamanne/python-environment-manager

"donjayamanne.python-environment-manager": {
    "disallowInstall": false,
    "extension": {
        "id": "ms-python.vscode-python-envs",
        "displayName": "Python Environments"
    }
}