Pin @octokit/request and @octokit/endpoint

[cyamonide]

Description

This PR attempts to resolve the is-plain-object dependency issue by following this comment: octokit/graphql.js#195 (comment)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[codecov]

Codecov Report

Merging #203 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #203   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            8         8           
  Lines          334       334           
  Branches        42        42           
=========================================
  Hits           334       334           

Flag	Coverage Δ
#unittests	100.00% <ø> (ø)

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