Update epubcheck-ruby requirement from 4.2.4.0 to 4.2.6.0#13

dependabot[bot] wants to merge 1 commit intomasterBPylypenko/progit2:masterfrom

dependabot/bundler/epubcheck-ruby-4.2.6.0BPylypenko/progit2:dependabot/bundler/epubcheck-ruby-4.2.6.0Copy head branch name to clipboard