Tweak code that uses refined so that it compiles with Scala 3

[fthomas]

This is in preparation for compiling with Scala 3 and probably the last chunk from #2065 that gets its own PR.

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.73%. Comparing base (dd4b207) to head (a84aba9).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...la/org/scalasteward/core/application/Context.scala	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3526   +/-   ##
=======================================
  Coverage   89.73%   89.73%           
=======================================
  Files         171      171           
  Lines        3536     3537    +1     
  Branches      321      330    +9     
=======================================
+ Hits         3173     3174    +1     
  Misses        363      363           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.