Fix http links in client-p4.asc (Chapter 9)

[HonkingGoose]

Which version of the book is affected?

Problem is with the files, present at master.

Describe the bug:

https://github.com/progit/progit2/blob/master/book/09-git-and-other-scms/sections/client-p4.asc still has http:// links instead of https:// links.

Also the links are probably not making sense anymore in the context of the text surrounding the links. Names and usage have changed, Git Fusion is now called Helix4Git apparently.

Steps to reproduce:

1. Go to https://github.com/progit/progit2/blob/master/book/09-git-and-other-scms/sections/client-p4.asc
2. Note there are still 4 http;// links.

Expected behavior:

Links use HTTPS.

Screenshots:

Additional context:

I'm closing #1210 in favor of this one.