Update specs2-core to 4.20.8

[scala-steward]

About this PR

📦 Updates org.specs2:specs2-core from 4.10.6 to 4.20.8

Usage

✅ Please merge!

I'll automatically update this PR to resolve conflicts as long as you don't change it yourself.

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⚙ Adjust future updates

Add this to your `.scala-steward.conf` file to ignore future updates of this dependency: ``` updates.ignore = [ { groupId = "org.specs2", artifactId = "specs2-core" } ] ``` Or, add this to slow down future updates of this dependency: ``` dependencyOverrides = [{ pullRequests = { frequency = "30 days" }, dependency = { groupId = "org.specs2", artifactId = "specs2-core" } }] ```

^{labels: test-library-update, early-semver-minor, semver-spec-minor, version-scheme:semver-spec, commit-count:1}

[scala-steward]

Superseded by #263.