Update scala to 2.12.21 (#206)

Co-authored-by: Kirill A. Korinsky <[email protected]>

Author: scala-steward

CHANGELOG.md

@@ -3,7 +3,7 @@
 All notable changes to this project will be documented in this file.
 
 ## [unreleased]
-- Switched to scala-2.12.20
+- Switched to scala-2.12.21
 - Switched to scala-2.13.18
 - Switched to scala-3.7.4
 - Switched to scalajs-1.20.1

build.sbt

@@ -2,7 +2,7 @@ import sbtcrossproject.CrossPlugin.autoImport.crossProject
 
 lazy val scala210 = "2.10.7"
 lazy val scala211 = "2.11.12"
-lazy val scala212 = "2.12.20"
+lazy val scala212 = "2.12.21"
 lazy val scala213 = "2.13.18"
 lazy val scala3 = "3.7.4"