Add importance of specifying [devName] for `okteto up`

[abs007]

The docs for okteto up needs some info that specifies the importance of using[devName] in okteto up.
https://www.okteto.com/docs/reference/cli/#up

[nitishfy]

I'd like to take this up. Please assign this issue to me.

[pchico83]

Thanks @nitishkumar06 !