fix uri in username with test environment oidc test

[durran]

Please complete the following before merging:

When implementing OIDC in the Ruby driver I noticed that the username with ENVIRONMENT:test spec test was not failing because of the username being present but rather the URI was actually invalid, since ENVIRONMENT:test was not in the authMechanismProperties. This fixes that test.

Tests running on this PR: mongodb/mongo-ruby-driver#2873

• Update changelog.
• Make sure there are generated JSON files from the YAML test files.
• Test changes in at least one language driver.
• Test these changes against all server versions and topologies (including standalone, replica set, sharded
  clusters, and serverless).

[blink1073]

Thanks!