fix: update Task::Alias to return command description

[jjjermiah]

[tasks]
hi = "echo hi"
hello = "echo hello"
welcome = { depends-on = ["hi", "hello"], description = "hi and hello" }

pixi task --manifest-path test_project/pixi.toml ls                      
Tasks that can run on this machine:
-----------------------------------
hello, hi, welcome

./target/pixi/release/pixi task --manifest-path test_project/pixi.toml ls
Tasks that can run on this machine:
-----------------------------------
hello, hi, welcome

 - welcome         hi and hello

[ruben-arts]

Thanks you!