Fix some Scala 3 errors

[fthomas]

This fixes some errors reported by Scala 3 (see https://github.com/scala-steward-org/scala-steward/pull/2065/checks?check_run_id=2383524444).

[codecov]

Codecov Report

Merging #2084 (e69893c) into master (13b0efc) will not change coverage.
The diff coverage is 83.33%.

@@           Coverage Diff           @@
##           master    #2084   +/-   ##
=======================================
  Coverage   78.16%   78.16%           
=======================================
  Files         131      131           
  Lines        2249     2249           
  Branches       51       53    +2     
=======================================
  Hits         1758     1758           
  Misses        491      491           

Impacted Files	Coverage Δ
...la/org/scalasteward/core/application/Context.scala	84.74% <0.00%> (ø)
...rc/main/scala/org/scalasteward/core/git/Sha1.scala	100.00% <ø> (ø)
...ala/org/scalasteward/core/application/Config.scala	97.29% <100.00%> (ø)
...main/scala/org/scalasteward/core/data/Update.scala	97.67% <100.00%> (ø)
...rd/core/repoconfig/PullRequestUpdateStrategy.scala	100.00% <100.00%> (ø)

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