Update proto version in README (#3666)

Fixes #3665

Author: ocelotl

opentelemetry-proto/README.rst

@@ -7,9 +7,9 @@ OpenTelemetry Python Proto
    :target: https://pypi.org/project/opentelemetry-proto/
 
 This library contains the generated code for OpenTelemetry protobuf data model. The code in the current
-package was generated using the v0.17.0 release_ of opentelemetry-proto.
+package was generated using the v0.20.0 release_ of opentelemetry-proto.
 
-.. _release: https://github.com/open-telemetry/opentelemetry-proto/releases/tag/v0.17.0
+.. _release: https://github.com/open-telemetry/opentelemetry-proto/releases/tag/v0.20.0
 
 Installation
 ------------