Here is the pull request: https://github.com/quasarframework/quasar/pull/740
I set the margin to 15px, because this is half the margin that is applied to a div.
I am not really sure about the class name because I do not know which naming conventions Quasar uses for CSS.

if you search for and remove this:

,(col.label)?_c('q-tooltip',{domProps:{"innerHTML":_vm._s(col.label)}}):_vm._e()

from quasar.esm.js (in two places: var TableContent and var TableSticky) you can remove them from all Data Tables. I found this a good solution for now until whenever the supposedly rewritten datatable component arrives.