Remove pydantic-settings as a dependency

[Devansh3712]

Use dotenv library's load_dotenv() function instead of pydantic-settings for loading environment variables from .env file

Checklist

• [x] Changes tested in container setup
• [x] Changes tested in non-containerized setup
• [ ] Includes tests
• [ ] Documentation updated

[kamoltat]

CI failure

#10 9.122 ERROR: Package 'teuthology-1.1.1.dev729-g861a8dcf' requires a different Python: 3.8.10 not in '>=3.10'
#10 ERROR: process "/bin/sh -c pip3 install -e ." did not complete successfully: exit code: 1
------
 > [6/7] RUN pip3 install -e .:
4.776 Collecting teuthology@ git+https://github.com/ceph/teuthology#egg=teuthology[test]
4.776   Cloning https://github.com/ceph/teuthology to /tmp/pip-install-g6d3wo0z/teuthology
4.776   Running command git clone -q https://github.com/ceph/teuthology /tmp/pip-install-g6d3wo0z/teuthology
6.291   Installing build dependencies: started
8.420   Installing build dependencies: finished with status 'done'
8.421   Getting requirements to build wheel: started
8.735   Getting requirements to build wheel: finished with status 'done'
8.739     Preparing wheel metadata: started
9.044     Preparing wheel metadata: finished with status 'done'
9.122 ERROR: Package 'teuthology-1.1.1.dev729-g861a8dcf' requires a different Python: 3.8.10 not in '>=3.10'
------
Dockerfile:24
--------------------
  22 |     WORKDIR /teuthology_api
  23 |     COPY . /teuthology_api/
  24 | >>> RUN pip3 install -e .
  25 |     RUN mkdir /archive_dir/
  26 |     
--------------------
ERROR: failed to solve: process "/bin/sh -c pip3 install -e ." did not complete successfully: exit code: 1
Service 'teuthology_api' failed to build : Build failed
Error: Process completed with exit code 1.

[Devansh3712]

sure, i'll amend the commit message