scripts/combo-layer: Fix deprecation warning

Resolve:
combo-layer:83: DeprecationWarning: This method will be removed in future versions.  Use 'parser.read_file()' instead.

(From OE-Core rev: 7b43e04424985cf71b9263969830c9e4e9d72e01)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/combo-layer

@@ -80,7 +80,7 @@ class Configuration(object):
         logger.debug("Loading config file %s" % self.conffile)
         self.parser = configparser.ConfigParser()
         with open(self.conffile) as f:
-            self.parser.readfp(f)
+            self.parser.read_file(f)
 
         # initialize default values
         self.commit_msg_template = "Automatic commit to update last_revision"