refactor: make properties for ParseGitHub, ParseLinkedIn lowercase

[cbaker6]

New Pull Request Checklist

• [x] I am not disclosing a vulnerability.
• [x] I am creating this PR in reference to an issue.

Issue Description

Recently added auth: ParseGitHub and ParseLinkedIn properties are cased gitHub and linkedIn respectively.

Related issue: #n/a

Approach

Make all casing lower case for properties named after their auth type. This makes of the ParseAuthentication auths look the same and makes it easier to copy/paste/modify new adapters in the future.

TODOs before merging

• [x] Add changes to documentation (guides, repository pages, in-code descriptions)

[parse-github-assistant[bot]]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[codecov[bot]]

Codecov Report

Merging #309 (f415143) into main (fdbb1d9) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #309   +/-   ##
=======================================
  Coverage   84.56%   84.56%           
=======================================
  Files         114      114           
  Lines       11661    11661           
=======================================
  Hits         9861     9861           
  Misses       1800     1800           

Impacted Files	Coverage Δ
...entication/3rd Party/ParseGithub/ParseGitHub.swift	100.00% <100.00%> (ø)
...cation/3rd Party/ParseLinkedIn/ParseLinkedIn.swift	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update fdbb1d9...f415143. Read the comment docs.