Womb owners is not an idiomatic expression, but it's absolutely clear who Jerry Lewis was referring to. As I woman, I don't find the expression particularly insulting nor offensive, but neither do I find it amusing. I do, however, interpret the comedian words as being snide and sarky in nature. To be brief he is saying that women shouldn't waste their time in telling jokes or kidding themselves they can do stand-up comedy, their primary function in life is to bear children.
After writing the above, I decided to read the Time article. Unbelievable. Jerry Lewis is the epitome of a male chauvinist pig. And that is all I have to say.