setup.cfg: update version metadata [skip ci]

Co-authored-by: Michael Hirsch <[email protected]>

Author: scivision

setup.cfg

@@ -23,10 +23,10 @@ classifiers =
   Operating System :: POSIX :: BSD
   Operating System :: POSIX :: Linux
   Programming Language :: Python :: 3 :: Only
-  Programming Language :: Python :: 3.5
   Programming Language :: Python :: 3.6
   Programming Language :: Python :: 3.7
   Programming Language :: Python :: 3.8
+  Programming Language :: Python :: 3.9
   Topic :: Software Development :: Build Tools
 long_description = Meson is a cross-platform build system designed to be both as fast and as user friendly as possible. It supports many languages and compilers, including GCC, Clang, PGI, Intel, and Visual Studio. Its build definitions are written in a simple non-Turing complete DSL.