[python-package] use f-strings for concatenation in examples/python-guide/logistic_regression.py

[sagnik1511]

Contributes to #4136.

Updated .\examples\python-guide\logistic_regression.py file

[jameslamb]

Thanks so much for this!

Please also change the following places:

• https://github.com/sagnik1511/LightGBM/blob/064e4868eca6fa893719dc50750d0a04cbc72e41/examples/python-guide/logistic_regression.py#L74
• https://github.com/sagnik1511/LightGBM/blob/064e4868eca6fa893719dc50750d0a04cbc72e41/examples/python-guide/logistic_regression.py#L84

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Some other general notes as well, which maintainers will appreciate in the future

• When you open a pull request, please reference any previous discussions in the description so that maintainers have enough context to understand the proposed changes. I've added "Contributes to Migrate to f-strings for the Python code #4136" to the PR description here.
• In the future, please use an informative title for your pull requests. This helps people to find it in the future from search, and makes the changelog for releases (e.g. https://github.com/microsoft/LightGBM/releases/tag/v3.2.1) easier to understand. "Migrated f-string codebase" is too broad. I've updated the title to be a bit more specific.
• In pull requests, it isn't necessary to explicitly write out what code changed. The PR description should just give a description of what you're proposing and why.

[sagnik1511]

Thanks so much for this!

Please also change the following places:

• https://github.com/sagnik1511/LightGBM/blob/064e4868eca6fa893719dc50750d0a04cbc72e41/examples/python-guide/logistic_regression.py#L74
• https://github.com/sagnik1511/LightGBM/blob/064e4868eca6fa893719dc50750d0a04cbc72e41/examples/python-guide/logistic_regression.py#L84

Some other general notes as well, which maintainers will appreciate in the future

• When you open a pull request, please reference any previous discussions in the description so that maintainers have enough context to understand the proposed changes. I've added "Contributes to Migrate to f-strings for the Python code #4136" to the PR description here.
• In the future, please use an informative title for your pull requests. This helps people to find it in the future from search, and makes the changelog for releases (e.g. https://github.com/microsoft/LightGBM/releases/tag/v3.2.1) easier to understand. "Migrated f-string codebase" is too broad. I've updated the title to be a bit more specific.
• In pull requests, it isn't necessary to explicitly write out what code changed. The PR description should just give a description of what you're proposing and why.

Thank you sir for your kind words. I've pulled a new request here. DO visit that :)

[github-actions]

This pull request has been automatically locked since there has not been any recent activity since it was closed. To start a new related discussion, open a new issue at https://github.com/microsoft/LightGBM/issues including a reference to this.