gst-validate: Fixed compatibility with Python 3.12

config.readfp() was removed in python 3.12 and config.read_file() does the same
thing and has been available since Python 3.2

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5624>

subprojects/gst-devtools/validate/launcher/baseclasses.py

@@ -2426,7 +2426,7 @@ class ScenarioManager(Loggable):
 
         config = configparser.RawConfigParser()
         f = open(scenario_defs)
-        config.readfp(f)
+        config.read_file(f)
 
         for section in config.sections():
             name = None