Update README.md (open-telemetry#28844)

The Prometheus Remote write exporter is missing the details of default
values for the remote write queue config. Added the values after looking
into the code for the same.

exporter/prometheusremotewriteexporter/README.md

@@ -53,9 +53,9 @@ The following settings can be optionally configured:
 - `namespace`: prefix attached to each exported metric name.
 - `add_metric_suffixes`: If set to false, type and unit suffixes will not be added to metrics. Default: true.
 - `remote_write_queue`: fine tuning for queueing and sending of the outgoing remote writes.
-  - `enabled`: enable the sending queue
-  - `queue_size`: number of OTLP metrics that can be queued. Ignored if `enabled` is `false`
-  - `num_consumers`: minimum number of workers to use to fan out the outgoing requests.
+  - `enabled`: enable the sending queue (default: `true`)
+  - `queue_size`: number of OTLP metrics that can be queued. Ignored if `enabled` is `false` (default: `10000`)
+  - `num_consumers`: minimum number of workers to use to fan out the outgoing requests. (default: `5`)
 - `resource_to_telemetry_conversion`
   - `enabled` (default = false): If `enabled` is `true`, all the resource attributes will be converted to metric labels by default.
 - `target_info`: customize `target_info` metric