.gitattributes: specify eol as LF

[SethFalco]

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page(s) have at most 8 examples.
• The page description(s) have links to documentation or a homepage.
• The page(s) follow the content guidelines.
• The PR title conforms to the recommended templates.
• Version of the command being documented (if known):

---

Above is N/A.

Replaces manual instructions with the .gitattributes config that should achieve the same thing. No manual commands or documentation necessary.

If we could just get someone on Windows to test if they can reproduce the original problem, and if this fixes it, we should be fine to merge this.

Related

• git-terminal.md: add instructions for CRLF on Windows #9010

[blueskyson]

Don't know about .gitattributes, but it looks rational.