Harmonize imports for http4s and circe literals

[fthomas]

This is in preparation for compiling with Scala 3 and prevents errors like

 -- [E008] Not Found Error: modules/core/src/test/scala/org/scalasteward/core/coursier/DependencyMetadataTest.scala:7:28
 7 |import org.http4s.implicits.http4sLiteralsSyntax
   |                            ^^^^^^^^^^^^^^^^^^^^
   | value http4sLiteralsSyntax is not a member of object org.http4s.implicits

and

 -- [E008] Not Found Error: modules/core/src/test/scala/org/scalasteward/core/forge/github/GitHubAuthAlgTest.scala:4:24
 4 |import io.circe.literal.JsonStringContext
   |                        ^^^^^^^^^^^^^^^^^
   |               value JsonStringContext is not a member of io.circe.literal

It also prefers importing org.http4s.syntax.literals._ over org.http4s.implicits._ so that we import less and are more explicit about what the import is about.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.73%. Comparing base (a114407) to head (ea708c1).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3521   +/-   ##
=======================================
  Coverage   89.73%   89.73%           
=======================================
  Files         171      171           
  Lines        3536     3536           
  Branches      321      321           
=======================================
  Hits         3173     3173           
  Misses        363      363           

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