Fixes LFS problem with conversable-agent.jpg

[davorrunje]

Why are these changes needed?

There is a problem with a file that should be tracked by LFS, but it is pushed as a regular file. The problem manifests itself in many scenarios, the simplest one being just cloning the repository:

$ git clone git@github.com:microsoft/autogen.git
Cloning into 'autogen'...
warning: templates not found in /home/davor/.git-template
remote: Enumerating objects: 97640, done.
remote: Counting objects: 100% (960/960), done.
remote: Compressing objects: 100% (244/244), done.
remote: Total 97640 (delta 426), reused 856 (delta 357), pack-reused 96680
Receiving objects: 100% (97640/97640), 470.24 MiB | 15.49 MiB/s, done.
Resolving deltas: 100% (47668/47668), done.
Updating files: 100% (547/547), done.
Filtering content: 100% (13/13), 6.04 MiB | 2.86 MiB/s, done.
Encountered 1 file that should have been a pointer, but wasn't:
    website/docs/tutorial/assets/conversable-agent.jpg

A recommended way to handle it is to run the following commands (https://docs.gitlab.com/ee/topics/git/lfs/troubleshooting.html):

$ git lfs migrate import --yes --no-rewrite website/docs/tutorial/assets/conversable-agent.jpg
$ git push

Related issue number

Closes #1973

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#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.