update ndoejs lambda docs to specify support of OTLP over HTTP only (#545)

Author: erichsueh3

src/docs/getting-started/lambda/lambda-js.mdx

@@ -45,6 +45,9 @@ Tips:
 * By default, the layer is configured to export traces to AWS X-Ray.
  Make sure your Lambda role has the required AWS X-Ray permissions.
   For more on AWS X-Ray permissions for AWS Lambda, see the [AWS Lambda documentation](https://docs.aws.amazon.com/lambda/latest/dg/services-xray.html#services-xray-permissions).
+* Also note that, the `OTEL_EXPORTER_OTLP_ENDPOINT` environment variable
+ does not need to be set. The default value is `http://localhost:4318`,
+  as the ADOT Node.JS lambda layer only supports OTLP over HTTP.
 
 ### Remove OpenTelemetry from your Lambda function
 To disable OpenTelemetry for your Lambda function, remove the Lambda layer,
@@ -54,7 +57,7 @@ remove the environment variable `AWS_LAMBDA_EXEC_WRAPPER`, and disable active tr
 
 ## Configuration
 
-The ADOT Node.js layer combines both OpenTelemetry JavaScript and the ADOT Collector.
+The ADOT Node.JS layer combines both OpenTelemetry JavaScript and the ADOT Collector.
 The configuration of the ADOT Collector follows the OpenTelemetry standard.
 
 By default, the ADOT Lambda layer uses the [config.yaml](https://github.com/aws-observability/aws-otel-lambda/blob/main/adot/collector/config.yaml),