deps: fix build for Python 3.6

Even though Python 3.6 had reached its EOL in 2021-12-23 [1], it doesn't
seem too hard to restore its support for now.

1. https://devguide.python.org/versions/

Author: DifferentialOrange

setup.py

@@ -87,6 +87,11 @@ def get_dependencies(filename):
 
 packages = [item for item in find_packages('.') if item.startswith('tarantool')]
 
+package_requirements = [
+    'packaging==21.3',
+    'setuptools_scm==6.4.2',
+]
+
 setup(
     name="tarantool",
     packages=packages,
@@ -110,9 +115,7 @@ def get_dependencies(filename):
     ],
     cmdclass=cmdclass,
     command_options=command_options,
-    install_requires=get_dependencies('requirements.txt'),
-    setup_requires=[
-        'setuptools_scm==6.4.2',
-    ],
+    install_requires=get_dependencies('requirements.txt') + package_requirements,
+    setup_requires=package_requirements,
     python_requires='>=3.6',
 )