[python] fix missing Any and Dict import when supporting addditionalProperties

[fa0311]

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Overview

fix #16151

[wing328]

Thanks for the PR. I've tested locally to confirm the fix, and filed the following to add a test to cover the issue moving forward.

#16218

Have a nice weekend.

[wing328]

@fa0311 thanks again for the PR. When you've time, can you please PM me via Slack: https://join.slack.com/t/openapi-generator/shared_invite/zt-12jxxd7p2-XUeQM~4pzsU9x~eGLQqX2g ?