Remove coverage; not supported on scala3

See scoverage/scalac-scoverage-plugin#299

build.sbt

@@ -10,20 +10,17 @@ val allScalaVersions = scala2Versions :+ scala3Version
 ThisBuild / scalaVersion := scala213
 ThisBuild / crossScalaVersions := allScalaVersions
 
-addCommandAlias("ci-test", "scalafmtCheckAll; scalafmtSbtCheck; mdoc; testCovered")
+addCommandAlias("ci-test", "scalafmtCheckAll; scalafmtSbtCheck; mdoc; ++test")
 addCommandAlias("ci-docs", "github; mdoc; headerCreateAll; publishMicrosite")
 addCommandAlias("ci-publish", "github; ci-release")
 
-coverageScalacPluginVersion := "1.4.8" // needed for scala 2.12.14
-
 publish / skip := true
 
 lazy val github4s = project
   .settings(coreDeps: _*)
   .settings(
     // Increase number of inlines, needed for circe semiauto derivation
-    scalacOptions ++= on(3, 9)(Seq("-Xmax-inlines", "20")).value.flatten,
-    coverageScalacPluginVersion := "1.4.8" // needed for scala 2.12.14
+    scalacOptions ++= on(3, 9)(Seq("-Xmax-inlines", "20")).value.flatten
   )
 
 //////////
@@ -37,14 +34,8 @@ lazy val microsite: Project = project
   .settings(micrositeSettings: _*)
   .settings(publish / skip := true)
   .settings(ScalaUnidoc / unidoc / unidocProjectFilter := inProjects(github4s, microsite))
-  .settings(
-    coverageScalacPluginVersion := "1.4.8" // needed for scala 2.12.14
-  )
 
 lazy val documentation = project
   .enablePlugins(MdocPlugin)
   .settings(mdocOut := file("."))
   .settings(publish / skip := true)
-  .settings(
-    coverageScalacPluginVersion := "1.4.8" // needed for scala 2.12.14
-  )