Update dependency ruby to v2.7.8

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
ruby (source)		patch	2.7.2 -> 2.7.8
ruby	final	patch	2.7.2 -> 2.7.8

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Configuration

📅 Schedule: Branch creation - "every weekend" in timezone Japan, Automerge - At any time (no schedule defined).

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about these updates again.

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.61%. Comparing base (4e8d71d) to head (c328083).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #44   +/-   ##
=======================================
  Coverage   53.61%   53.61%           
=======================================
  Files          13       13           
  Lines         981      981           
=======================================
  Hits          526      526           
  Misses        391      391           
  Partials       64       64           

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