[refactor] Address the unnecessary dependent gem issues

[brgnepal]

I recently came to know that we are using unnecessary dependent gems which comes with github-pages gem.

See more in the comment https://github.com/USRSE/usrse.github.io/issues/424#issuecomment-802603030.

My standard Gemfile has these much content:

gem "jekyll", "~> 4.1.1"
gem 'html-proofer'

group :jekyll_plugins do
  gem "jekyll-seo-tag"
  gem "jekyll-paginate-v2"
  gem "jekyll-redirect-from"
end

This issue is created to address the refactoring of the Gemfile.

NOTE: We might need to be careful while doing it.

[vsoch]

This would be easy to tackle soon - do you want to take charge of it @coolbrg? I would be happy to review!

[brgnepal]

do you want to take charge of it @coolbrg?

Ya sure. 👍

[kescobo]

Based on the end of the conversation in #427, it looks like this is no longer an issue? Closing for now