[BugFix] python version

[ShuN6211]

Enable to run "poetry install".

Description

Update pyproject.toml to be enable to run poetry install and install rl4co project by poetry tool.
At current project, running poetry install may causes following errors.

The current project's Python requirement (>=3.9) is not compatible with some of the required packages Python requirement:

• pyvrp requires Python <4.0,>=3.9, so it will not be satisfied for Python >=4.0
• pyvrp requires Python <4.0,>=3.9, so it will not be satisfied for Python >=4.0
• pyvrp requires Python <4.0,>=3.9, so it will not be satisfied for Python >=4.0
  Because no versions of pyvrp match >0.8.2,<0.9.0 || >0.9.0,<0.9.1 || >0.9.1
  and pyvrp (0.8.2) requires Python <4.0,>=3.9, pyvrp is forbidden.
  And because pyvrp (0.9.0) requires Python <4.0,>=3.9, pyvrp is forbidden.
  So, because pyvrp (0.9.1) requires Python <4.0,>=3.9
  and rl4co depends on pyvrp (>=0.8.2), version solving failed.
  • Check your dependencies Python requirement: The Python requirement can be specified via the python or markers properties
  For pyvrp, a possible solution would be to set the python property to ">=3.9,<4.0"
  For pyvrp, a possible solution would be to set the python property to ">=3.9,<4.0"
  For pyvrp, a possible solution would be to set the python property to ">=3.9,<4.0"

Motivation and Context

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

What types of changes does your code introduce? Remove all that do not apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)
• Example (update in the folder of examples)

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.