build: update python to v3.9 and ray to v2.7

[dimakis]

Issue link

closes #371

What changes have been made

Update python and ray versions

Verification steps

1. Checkout PR
2. Build python wheel using poetry build. Wheel should be in the dist folder.
3. Install the wheel on your cluster
4. run through the demo notebooks
5. the nbs should run as expected

Checks

• I've made sure the tests are passing.
• Testing Strategy
  • Unit tests
  • Manual tests
  • Testing is not required for this change

[dimakis]

@KPostOffice @MichaelClifford

I've not had time to update the entire code, this is the image rayproject/ray:latest-py39-cu118

but I've tested it with 3 demo notebooks

[Bobbins228]

Tested this out on multiple notebooks including local_interactive and works as intended.
Ray ver is 2.7 as expected and the custom ray image works for me.
Good stuff
/LGTM

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