Revert "Update CRT (#522)" (#526)

This reverts commit cb9dd6b.

Author: sfod

lib/eventstream_rpc_utils.spec.ts

@@ -20,15 +20,7 @@ import {CrtError, eventstream} from "aws-crt";
  * @return a base64-encoded string
  */
 export function encodePayloadAsString(payload : eventstream.Payload) : string {
-    if (ArrayBuffer.isView(payload)) {
-        return Buffer.from(payload.buffer, payload.byteOffset, payload.byteLength).toString("base64");
-    } else if (typeof payload === "string") {
-        let value = payload as string;
-        return Buffer.from(value).toString("base64");
-    } else {
-        let value = payload as ArrayBuffer;
-        return Buffer.from(value).toString("base64");
-    }
+    return Buffer.from(payload).toString("base64");
 }
 
 /**