Cleanup: remove redundant encoding and default open mode

Doc/tools/extensions/c_annotations.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 """
     c_annotations.py
     ~~~~~~~~~~~~~~~~
@@ -62,7 +61,7 @@ def __init__(self, name):
 class Annotations:
     def __init__(self, refcount_filename, stable_abi_file):
         self.refcount_data = {}
-        with open(refcount_filename, 'r') as fp:
+        with open(refcount_filename) as fp:
             for line in fp:
                 line = line.strip()
                 if line[:1] in ("", "#"):
@@ -90,7 +89,7 @@ def __init__(self, refcount_filename, stable_abi_file):
                     entry.result_refs = refcount
 
         self.stable_abi_data = {}
-        with open(stable_abi_file, 'r') as fp:
+        with open(stable_abi_file) as fp:
             for record in csv.DictReader(fp):
                 name = record['name']
                 self.stable_abi_data[name] = record