Update grpc-netty, grpc-protobuf, grpc-stub to 1.68.3 (#1799)

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

Author: scala-steward

project/Dependencies.scala

@@ -4,7 +4,7 @@ import Keys._
 
 object Dependencies {
   object versions {
-    val grpc                 = "1.68.2"
+    val grpc                 = "1.68.3"
     val protobuf             = "4.28.2"
     val silencer             = "1.7.19"
     val collectionCompat     = "2.12.0"