Update scala-compiler, scala-library, ... to 2.12.21 (#1429)

Author: scala-steward

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        scala: [2.12.20, 2.13.18]
+        scala: [2.12.21, 2.13.18]
         java: [temurin@8]
         platform: [jvm, js, native]
     runs-on: ${{ matrix.os }}

build.sbt

@@ -1,7 +1,7 @@
 import com.github.sbt.git.SbtGit.GitKeys.*
 import sbtcrossproject.CrossProject
 
-val Scala212 = "2.12.20"
+val Scala212 = "2.12.21"
 val Scala213 = "2.13.18"
 
 commonSettings