[3.14] Fix typos in Doc/extending/extending.rst and Doc/library/shelve.rst (pythonGH-136890)

(cherry picked from commit 80a7017)

Co-authored-by: Cornelius Roemer <[email protected]>

Author: corneliusroemer

Doc/extending/extending.rst

@@ -214,7 +214,7 @@ and initialize it by calling :c:func:`PyErr_NewException` in the module's
 
    SpamError = PyErr_NewException("spam.error", NULL, NULL);
 
-Since :c:data:`!SpamError` is a global variable, it will be overwitten every time
+Since :c:data:`!SpamError` is a global variable, it will be overwritten every time
 the module is reinitialized, when the :c:data:`Py_mod_exec` function is called.
 
 For now, let's avoid the issue: we will block repeated initialization by raising an

Doc/library/shelve.rst

@@ -116,7 +116,6 @@ Restrictions
 * On macOS :mod:`dbm.ndbm` can silently corrupt the database file on updates,
   which can cause hard crashes when trying to read from the database.
 
-
 .. class:: Shelf(dict, protocol=None, writeback=False, keyencoding='utf-8')
 
    A subclass of :class:`collections.abc.MutableMapping` which stores pickled