Pre-release: Update version to 0.4.0 (#246)

This PR updates the version to 0.4.0.

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Co-authored-by: github-actions <[email protected]>

Author: aws-application-signals-bot

aws-opentelemetry-distro/src/amazon/opentelemetry/distro/version.py

@@ -1,4 +1,4 @@
 # Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 # SPDX-License-Identifier: Apache-2.0
 
-__version__ = "0.3.0.dev0"
+__version__ = "0.4.0"