Bump version to 0.7

[marklysze]

Why are these changes needed?

Version 0.7

Related issue number

N/A

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/docs/contributor-guide/documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[marklysze]

Working with @davorrunje on the failing test.

[marklysze]

Fail was intermittent, likely due to OpenAI/environment.