Upgrade to 2.0 version of google-gemini-php

Hi @dmundra

There is an active issue ([3519469]) for tools calling, which I think pretty much involves everything in this issue. So, I will set this as a related one and once we merge the tools calling (there is an open MR there), we can mark this as fixed too.

Thank you for the help and if you are available you can continue to contribute to the tools calling issue.

Thank you @jibla for linking the issue. I can try to test that.