[python-package] use f-strings for concatenation in examples/python-guide/logistic_regression.py (#4356)
[python-package] use f-strings for concatenation in examples/python-guide/logistic_regression.py (#4356)

* updated with f-string migration

* Update logistic_regression.py

* Update logistic_regression.py

* Update logistic_regression.py

* Update logistic_regression.py
microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM,henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM