Change topic name size from 25 to 50

[lunny]

Fix #14108

[zeripath]

I think we should just make this 255

[lafriks]

What is the max size for github?

[6543]

@lunny created backportable fix: #14152

this pull should still go in too :)

[zeripath]

What is the max size for github?

I'm not sure that there is one. I got it up to 100 characters without a problem. Let me take a look at pathological.

Error saving your changes: Repository topics Topics must start with a lowercase letter or number, consist of 35 characters or less, and can include hyphens.

So 35.

[zeripath]

Although I suspect that we could easily get away with 255 here - 50 appears to be enough to cope with Github