gh-156226: Fix doubled-word typos in docs and comments

- Doc/library/difflib.rst: 'produced in in various formats'
- Lib/multiprocessing/resource_tracker.py: 'we encode encode the raw name bytes'
- Lib/test/test_exception_group.py: 'Is is also used' -> 'It is also used'
- Lib/test/test_unittest/testmock/testhelpers.py: 'isn't isn't callable'

Author: zaveshaa

Doc/library/difflib.rst

@@ -17,7 +17,7 @@ This module provides classes and functions for comparing sequences.
 Most of them compare sequences of text lines (for example lists of strings,
 or :term:`file objects <file object>`) and
 produce :dfn:`diffs` -- reports on the differences.
-Diffs can be produced in in various formats, including HTML and context
+Diffs can be produced in various formats, including HTML and context
 and unified diffs -- formats produced by tools like
 :manpage:`diff <diff(1)>` and :manpage:`git diff <git-diff(1)>`.
 

Lib/multiprocessing/resource_tracker.py

@@ -359,7 +359,7 @@ def _send(self, cmd, name, rtype):
         # With json.dump(..., ensure_ascii=True) every non-ASCII byte becomes a 6-char
         # escape like \uDC80.
         # As we want the overall message to be kept atomic and therefore smaller than 512,
-        # we encode encode the raw name bytes with URL-safe Base64 - so a 255 long name
+        # we encode the raw name bytes with URL-safe Base64 - so a 255 long name
         # will not exceed 340 bytes.
         b = name.encode('utf-8', 'surrogateescape')
         if len(b) > 255:

Lib/test/test_exception_group.py

@@ -583,7 +583,7 @@ def leaf_generator(exc, tbs=None):
 
 class LeafGeneratorTest(unittest.TestCase):
     # The leaf_generator is mentioned in PEP 654 as a suggestion
-    # on how to iterate over leaf nodes of an EG. Is is also
+    # on how to iterate over leaf nodes of an EG. It is also
     # used below as a test utility. So we test it here.
 
     def test_leaf_generator(self):

Lib/test/test_unittest/testmock/testhelpers.py

@@ -687,7 +687,7 @@ def f(self, y): pass
         self.assertRaises(TypeError, instance_mock.a, 'foo', 'bar')
         self.assertRaises(AttributeError, getattr, instance_mock, 'b')
 
-        # The return value isn't isn't callable
+        # The return value isn't callable
         self.assertRaises(TypeError, instance_mock)
 
         instance_mock.Bar.f(6)