Update pprof dependency

[salarali]

Would it be possible to update the pprof dependency? Its pretty old.

[felixge]

Yeah, I can update it. But before I do, is there a reason you're asking? What improvements are you hoping for? Thanks

[salarali]

Nothing is particular. Was just checking the go.mod file and saw that it was pretty old.

I was going through the commits since then and something like this would be nice
google/pprof#729