Update coursier to 2.1.21 (#1785)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: scala-steward

project/Dependencies.scala

@@ -8,7 +8,7 @@ object Dependencies {
     val protobuf             = "4.28.2"
     val silencer             = "1.7.19"
     val collectionCompat     = "2.12.0"
-    val coursier             = "2.1.20"
+    val coursier             = "2.1.21"
     val protocGen            = "0.9.8"
     val protobufRuntimeScala = "0.8.16"
     val commonsCodec         = "1.17.1"