Fix "Stream must be replayable to calculate a body hash" error

Author: lauzadis

runtime/serde/serde-cbor/common/src/aws/smithy/kotlin/runtime/serde/cbor/CborSerializer.kt

@@ -27,7 +27,7 @@ public class CborSerializer :
     StructSerializer {
     private val buffer = SdkBuffer()
 
-    public fun toHttpBody(): HttpBody = buffer.toHttpBody(contentLength = buffer.size)
+    public fun toHttpBody(): HttpBody = buffer.readByteArray().toHttpBody()
 
     override fun toByteArray(): ByteArray = buffer.readByteArray()