Uninstall symlink cleanup

[luraess]

On macOS arm64, it seems that uninstalling Juliaup fails to delete symlinks in .local if present. As a result, the successive installs of Julia via Juliaup with symlink for channel-specific version fails to create the symlink as the "file already exists":

Error: Failed to run `run_command_add`.

Caused by:
    0: failed to create symlink `/Users/ludovic/.local/bin/julia-release`.
    1: File exists (os error 17)