Remove incorrect version for octokit

[utkarsh2102]

Hey,

I don't think octokit 4.2 will work with for the test.
There's 4.13 out now. Could you please patch the same?

jekyll-gist/jekyll-gist.gemspec

Line 24 in ca86372

spec.add_dependency "octokit", "~> 4.2"

Or I can send a PR for the same?

[utkarsh2102]

Or can it be >=4.2?

[ashmaroli]

@utkarsh2102 4.13 is not a subset of 4.1.
"~> 4.2" means any version between 4.2.0 and 5.0.0