Increase time to wait for git in the git vcs class

[nover]

Once in a while, I'm challenged by by PGP key entry, and I simply cannot enter the code fast enough before dotnet version bails out.

It turns out that GitVcs.LaunchGitWithArgs passes along a wait-timeout of just 1 second to the git command line, and thus it aborts.

I think we can safely increase this to 10 or 20 seconds, to allow people to enter PGP keys or other things that git might ask for, before we fail the version bump.