fix the name in find query

[mosaicthej]

The .config installed by github's fast_float, makes the library to be exposed as FastFloat, not fast_float.

So current situation is that no matter if the library exist or not, it pulls from github remote anyways.

Also updated the version to be 6.1.3 as it's the newest release.

Description

Fixes # (issue)

The current CMakeLists would pull fast_float from github anyways irrespective if the library is installed or not.

I changed the NAME field to FastFloat so it would pick up if previously has been installed.

Type of change

• [x] Housekeeping

How Has This Been Tested?

Tested with a clean install of fast_float library, then build stellarium. When change the NAME, cmake won't pull from remote.

Test Configuration:

• Operating system:
• • OS: Gentoo Linux x86_64
• • Kernel: 6.10.0-gentoo-x86_64
• Graphics Card: Intel Raptor Lake-P [Iris Xe Graphics], 13th Gen Intel i9-13900H (20) @ 5.200GHz

Checklist:

• [x] My code follows the code style of this project.
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation (header file)
• [ ] I have updated the respective chapter in the Stellarium User Guide
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules