bump minimum python version to 3.7 (#61)

Author: jfsantos-ds

setup.py

@@ -36,7 +36,7 @@
       keywords='data science ydata',
       url='https://github.com/ydataai/ydata-quality',
       license="https://github.com/ydataai/ydata-quality/blob/master/LICENSE",
-      python_requires=">=3.6, <3.9",
+      python_requires=">=3.7, <3.9",
       packages=find_namespace_packages('src'),
       package_dir={'':'src'},
       include_package_data=True,