fix: decrease max buffered amount for WebRTC datachannels (#2628)

From experimental testing, 16MB is too big for Chrome to handle,
when sending large amounts of data - the `bufferedamountlow` never
fires.

Lower it to 2MB which seems to work better when running the Helia
transport benchmarks.

packages/transport-webrtc/src/stream.ts

@@ -27,7 +27,7 @@ export interface WebRTCStreamInit extends AbstractStreamInit, DataChannelOptions
 /**
  * How much can be buffered to the DataChannel at once
  */
-export const MAX_BUFFERED_AMOUNT = 16 * 1024 * 1024
+export const MAX_BUFFERED_AMOUNT = 2 * 1024 * 1024
 
 /**
  * How long time we wait for the 'bufferedamountlow' event to be emitted