Fix typos in config support info

[EliahKagan]

This fixes #1530 and makes some other minor improvements.

• core.looseCompression - use canonical capitalization for key
• core.packedGitLimit - work well on 64-bit, not 32-bit (#1530)
• core.sparseCheckoutCone - fix misspelled sparseCheckout ref
• submodule.recurse - fix minor spelling typo

Further improvements are possible, such as to unify the style of the explanations so that they all follow the same capitalization and quoting conventions. I believe that should be done, but since I may inquire about other substantive areas soon anyway (as I did in #1530), I think that can wait until a subsequent PR.

This information is available by API, so maybe this should be a conventional commit? I can easily amend this so the commit message starts with fix: if you like. This seems like a gray area with respect to whether fix: ought to be used.

[EliahKagan]

I've opened #1537 for those further changes.