bump constraint on meson-python version

it should be at least 0.18 to allow license in the format of the PR

Author: dimpase

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["meson-python>=0.15.0", "cython>=3.0", "cysignals>=1.11.3"]
+requires = ["meson-python>=0.18.0", "cython>=3.0", "cysignals>=1.11.3"]
 build-backend = "mesonpy"
 
 [project]