Update scala-library to 2.12.21

Author: scala-steward

.github/workflows/ci.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        scala: ["2.12.20", "2.13.15", "3.3.7"]
+        scala: ["2.12.21", "2.13.15", "3.3.7"]
     steps:
       - uses: actions/checkout@v2
       - uses: coursier/cache-action@v6

build.sbt

@@ -19,8 +19,8 @@ inThisBuild(
   )
 )
 
-scalaVersion       := "2.12.20"
-crossScalaVersions := Seq("2.12.20", "2.13.15", "3.3.7")
+scalaVersion       := "2.12.21"
+crossScalaVersions := Seq("2.12.21", "2.13.15", "3.3.7")
 
 libraryDependencies ++=
   Seq(