It just means you are physically required to perform the operation - work that is automated is not physically done by anyone, and where it gets confusing is we both provide the automation yet are required to keep it running.
Heroku and other PaaS systems eliminate server administration and scaling for many companies. That same work is still fundamental and critical for organizations like Amazon. But it is really just an inefficiency we are learning how to automate completely, with manual labor in the interim.
>manual work is physical work done by people, most especially in contrast to that done by machines, and also to that done by working animals.
Here, inconveniently, "physical" is left undefined. And in fact, it's being used to mean "non-linguistic/non-social."