Remove conversion methods that acctually already existed and worked in standard library

multiplatform-crypto-api/src/commonMain/kotlin/com/ionspin/kotlin/crypto/util/ConversionUtil.kt

@@ -1,16 +0,0 @@
-package com.ionspin.kotlin.crypto.util
-
-/**
- * Created by Ugljesa Jovanovic
- * ugljesa.jovanovic@ionspin.com
- * on 22-Jun-2020
- */
-@Suppress("CAST_NEVER_SUCCEEDS")
-fun ByteArray.asUByteArray() : UByteArray {
-    return this as UByteArray
-}
-
-@Suppress("CAST_NEVER_SUCCEEDS")
-fun UByteArray.asByteArray() : ByteArray {
-    return this as ByteArray
-}