Revert "Update default OTLP http port (open-telemetry#939)"

This reverts commit 05444a8.

Author: ThomsonTan

exporters/otlp/README.md

@@ -44,10 +44,9 @@ auto exporter = std::unique_ptr<sdktrace::SpanExporter>(new otlp::OtlpHttpExport
 
 ### Configuration options
 
-| Option                               | Default          |
-| ------------------------------------ |----------------- |
-| `OtlpGrpcExporterOptions.endpoint`   | `localhost:4317` |
-| `OtlpHttpExporterOptions.endpoint`   | `localhost:4318` |
+| Option       | Default          |
+| ------------ |----------------- |
+| `endpoint`   | `localhost:4317` |
 
 ## Example
 

exporters/otlp/include/opentelemetry/exporters/otlp/otlp_http_exporter.h

@@ -50,7 +50,7 @@ struct OtlpHttpExporterOptions
   // @see
   // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/otlp.md
   // @see https://github.com/open-telemetry/opentelemetry-collector/tree/main/receiver/otlpreceiver
-  std::string url = std::string("http://localhost:4318") + kDefaultTracePath;
+  std::string url = std::string("http://localhost:4317") + kDefaultTracePath;
 
   // By default, post json data
   HttpRequestContentType content_type = HttpRequestContentType::kJson;