Deprecate pytoml to reduce the unnecessary dependency due to no longer maintain

[ElliotNguyen68]

Description

Hi team, we are using lightgbm in production environment, but for CI process, we encounter a weird situation with pytoml.

Reproducible example

`Starting: Install packages for unit test

Task : Command line
Description : Run a command line script using Bash on Linux and macOS and cmd.exe on Windows
Version : 2.250.1
Author : Microsoft Corporation
Help : https://docs.microsoft.com/azure/devops/pipelines/tasks/utility/command-line

Generating script.
========================== Starting Command Output ===========================
/usr/bin/bash --noprofile --norc /home/vsts/work/_temp/2619a5f7-ba0f-4c44-aef4-adace077ecf2.sh
Requirement already satisfied: pip in /opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages (25.0.1)
Requirement already satisfied: setuptools in /opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages (56.0.0)
Collecting setuptools
Downloading setuptools-75.3.2-py3-none-any.whl.metadata (6.9 kB)
Collecting wheel
Downloading wheel-0.45.1-py3-none-any.whl.metadata (2.3 kB)
Downloading setuptools-75.3.2-py3-none-any.whl (1.3 MB)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 1.3/1.3 MB 98.7 MB/s eta 0:00:00
Downloading wheel-0.45.1-py3-none-any.whl (72 kB)
Installing collected packages: wheel, setuptools
Attempting uninstall: setuptools
Found existing installation: setuptools 56.0.0
Uninstalling setuptools-56.0.0:
Successfully uninstalled setuptools-56.0.0
Successfully installed setuptools-75.3.2 wheel-0.45.1
Collecting pypandoc==1.4
Downloading pypandoc-1.4.tar.gz (27 kB)
Preparing metadata (setup.py): started
Preparing metadata (setup.py): finished with status 'done'
Building wheels for collected packages: pypandoc
Building wheel for pypandoc (setup.py): started
Building wheel for pypandoc (setup.py): finished with status 'done'
Created wheel for pypandoc: filename=pypandoc-1.4-py3-none-any.whl size=16455 sha256=e8acd30d02ad5d61b0f334777f0669a41289bdcb0890c9e77911102fd7ba6b8e
Stored in directory: /home/vsts/.cache/pip/wheels/f7/d9/a0/ef1fe56c058e41d6271a4935caaeae89d43e2280504690a329
Successfully built pypandoc
Installing collected packages: pypandoc
Successfully installed pypandoc-1.4
Collecting pip==20.0.2 (from -r ./dev-requirements.txt (line 1))
Downloading pip-20.0.2-py2.py3-none-any.whl.metadata (3.4 kB)
Collecting coverage==7.0.1 (from -r ./dev-requirements.txt (line 2))
Downloading coverage-7.0.1-cp38-cp38-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_17_x86_64.manylinux2014_x86_64.whl.metadata (9.5 kB)
`

Environment info

LightGBM version or commit hash:

Command(s) you used to install LightGBM

Additional Comments

[jameslamb]

Closing this as duplicate and locking it, as you immediately opened an identical issue right after this. In the future, please do be careful not to do this.