Remove deprecated exporters (#1920)

* Remove deprecated exporters

* Update PR number in changelog entry

Author: MrAlias

CHANGELOG.md

@@ -20,6 +20,12 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Fix the `echo` middleware by using `SpanKind.SERVER` when deciding the `SpanStatus`.
   This makes `4xx` response codes to not be an error anymore. (#1848)
 
+### Removed
+
+- The deprecated `go.opentelemetry.io/contrib/exporters/metric/datadog` module is removed. (#1920)
+- The deprecated `go.opentelemetry.io/contrib/exporters/metric/dogstatsd` module is removed. (#1920)
+- The deprecated `go.opentelemetry.io/contrib/exporters/metric/cortex` module is removed.
+  Use the `go.opentelemetry.io/otel/exporters/otlp/otlpmetric` exporter as a replacement to send data to a collector which can then export with its PRW exporter. (#1920)
 
 ## [1.4.0/0.29.0] - 2022-02-14