Fix bundle install llhttp-ffi

Related issue: #5 (closed)

Fix bundle install on llhttp-ffi.

Failed job case: https://jihulab.com/gitlab-cn/code-sync/-/jobs/5892395

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
current directory:
/builds/gitlab-cn/code-sync/gitlab/vendor/ruby/2.7.0/gems/llhttp-ffi-0.4.0/ext
/usr/local/bin/ruby -I/usr/local/lib/ruby/site_ruby/2.7.0 -rrubygems
/builds/gitlab-cn/code-sync/gitlab/vendor/ruby/2.7.0/gems/rake-13.0.6/exe/rake
RUBYARCHDIR\=/builds/gitlab-cn/code-sync/gitlab/vendor/ruby/2.7.0/extensions/x86_64-linux/2.7.0/llhttp-ffi-0.4.0
RUBYLIBDIR\=/builds/gitlab-cn/code-sync/gitlab/vendor/ruby/2.7.0/extensions/x86_64-linux/2.7.0/llhttp-ffi-0.4.0
rake aborted!
LoadError: libffi.so.6: cannot open shared object file: No such file or
directory -
/builds/gitlab-cn/code-sync/gitlab/vendor/ruby/2.7.0/gems/ffi-1.15.5/lib/ffi_c.so

An error occurred while installing llhttp-ffi (0.4.0), and Bundler cannot
continue.
In Gemfile:
  kubeclient was resolved to 4.9.4.pre.gitlab1, which depends on
    http was resolved to 5.1.1, which depends on
      llhttp-ffi

Background

Upstream related MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/107171/diffs#f20c44b9d61f8b5946386c2345300e3b835c59c1

Due to the conflict of http Gem dependencies,

Upstream saved kubeclient Gem to the vendor directory and modified the version of the http Gem in it.