Issue #27626: Spelling fixes in docs, comments and internal names

Based on patch by Ville Skyttä.
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index e73d8ee..4265bc2 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1900,7 +1900,7 @@
    On Unix, *path* can be of type :class:`str` or :class:`bytes` (use
    :func:`~os.fsencode` and :func:`~os.fsdecode` to encode and decode
    :class:`bytes` paths). On Windows, *path* must be of type :class:`str`.
-   On both sytems, the type of the :attr:`~DirEntry.name` and
+   On both systems, the type of the :attr:`~DirEntry.name` and
    :attr:`~DirEntry.path` attributes of each :class:`DirEntry` will be of
    the same type as *path*.