Remove vestigial safe call in jvm Exceptions.kt (#4406)

Author: kyay10

kotlinx-coroutines-core/jvm/src/Exceptions.kt

@@ -68,9 +68,6 @@ internal actual class JobCancellationException public actual constructor(
         other === this ||
             other is JobCancellationException && other.message == message && other.job == job && other.cause == cause
 
-    override fun hashCode(): Int {
-        // since job is transient it is indeed nullable after deserialization
-        @Suppress("UNNECESSARY_SAFE_CALL")
-        return (message!!.hashCode() * 31 + (job?.hashCode() ?: 0)) * 31 + (cause?.hashCode() ?: 0)
-    }
+    override fun hashCode(): Int =
+        (message!!.hashCode() * 31 + job.hashCode()) * 31 + (cause?.hashCode() ?: 0)
 }