Fix 'git' brand letter casing

[hsnabszhdn]

Heads-up: Potentially a spicy topic (open to discussion and even rejection)

Although the Git logo is all lowercase, i.e. "git", the textual representation of the project is "Git":

"[...] the use of the term "Git" and the logos [...]"

When used as a general text, it should be used like this:

Create a Git repository

When used as a CLI command, it should be used like this (lowercase backtick'd):

Use the git command line

To see proper examples, search for git in the official Git - Getting a Git Repository document to see what I mean.

I understand that both "git" and "Git" are generally used in online articles or product documentations. However, the usage here is an expert-written formal spec and standard.

I believe it should reflect professionalism and attention to details, and not follow the general "what everyone else does" pattern, but again it's more of a personal opinion than what's "right" or "wrong". So, up to the maintainers what to do with this PR...

⚖️ Disclaimer: I'm not a lawyer and it's not a legal advice. I'm just an engineer talking based on what I've seen/read around the Internet. It's up to the core maintainers to consider proper use and permissions of all trademarks. I take no responsibility for copyright infringements, trademark usage violations, or any financial/collateral damage (if any).