setup.cfg: migrate more settings from pbr to built-in setuptools config

In pypa/setuptools#2712 setuptools learned to natively
support globbing data files, and the pbr setting to do the exact same thing is
not needed anymore. Pin the minimum build requirement to ensure the correct
version is used.

setup.cfg

@@ -24,13 +24,13 @@ packages =
     guake
 setup_requires =
     pbr
+    setuptools>=57.5.0
 install_requires =
     importlib_metadata; python_version < '3.8'
     typing; python_version < '3.5'
 
-[files]
-data_files =
-    share/guake/po = po/*
+[options.data_files]
+share/guake/po = po/*
 
 [options.entry_points]
 console_scripts =