Bump alpine to 3.21

Author: Gedochao

project/deps/package.mill.scala

@@ -282,7 +282,7 @@ def buildCsM1Version = Deps.Versions.coursierM1Cli
 // Native library used to encrypt GitHub secrets
 def libsodiumVersion = "1.0.20"
 // Using the libsodium static library from this Alpine version (in the static launcher)
-def alpineVersion = "3.16"
+def alpineVersion = "3.21"
 def ubuntuVersion = "24.04"
 
 object Docker {