Fix typo in WebTransportBidirectionalStream subfeature (#28711)

Author: caugner

api/WebTransportBidirectionalStream.json

@@ -102,7 +102,7 @@
         },
         "returns_WebTransportReceiveStream": {
           "__compat": {
-            "description": "Returns `WebTransportReceiveStream` (earlier spec returned `WritableStream`)",
+            "description": "Returns `WebTransportReceiveStream` (earlier spec returned `ReadableStream`)",
             "spec_url": "https://w3c.github.io/webtransport/#dom-webtransportbidirectionalstream-readable",
             "tags": [
               "web-features:webtransport"