fix: revert to python:3.10-slim base image for AutoGen Studio

[gunt3001]

Why are these changes needed?

This reverts the base image in AutoGen Studio Dockerfile to FROM python:3.10-slim. This fixes the Docker image build failure due to conflicting UID with Dev Container's vscode user.

Related issue number

Fixes #5929

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md 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.

[gunt3001]

@microsoft-github-policy-service agree

[victordibia]

Thanks @gunt3001 , looking good.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.56%. Comparing base (3b1ed78) to head (7704a8a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5932   +/-   ##
=======================================
  Coverage   75.56%   75.56%           
=======================================
  Files         191      191           
  Lines       13093    13093           
=======================================
  Hits         9894     9894           
  Misses       3199     3199           

Flag	Coverage Δ
unittests	75.56% <ø> (ø)

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