CHORE: fix pyproject.toml deprecated usages of license information

Author: Valentin-Laurent

pyproject.toml

@@ -9,7 +9,8 @@ name = "MAPIE"
 version = "0.9.2"
 description = "A scikit-learn-compatible module for estimating prediction intervals."
 readme = "README.rst"
-license = {file = "LICENSE"}
+license = "BSD-3-Clause"
+license-files = ["LICENSE"]
 maintainers = [
     {name = "Valentin Laurent", email = "valentin.laurent@capgemini.com"},
     {name = "Thibault Cordier", email = "thibault.a.cordier@capgemini.com"},
@@ -25,7 +26,6 @@ dependencies = [
 classifiers = [
     "Intended Audience :: Science/Research",
     "Intended Audience :: Developers",
-    "License :: OSI Approved",
     "Topic :: Software Development",
     "Topic :: Scientific/Engineering",
     "Operating System :: Microsoft :: Windows",