Spelling fixes to docs, docstrings, and comments (GH-6374)

(cherry picked from commit 61f82e0e337f971da57f8f513abfe693edf95aa5)

Co-authored-by: Ville Skyttä <ville.skytta@iki.fi>
diff --git a/Python/fileutils.c b/Python/fileutils.c
index 32aeea4..35869c8 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -431,7 +431,7 @@
    can be decoded as a surrogate character, escape the bytes using the
    surrogateescape error handler instead of decoding them.
 
-   On sucess, return 0 and write the newly allocated wide character string into
+   On success, return 0 and write the newly allocated wide character string into
    *wstr (use PyMem_RawFree() to free the memory). If wlen is not NULL, write
    the number of wide characters excluding the null character into *wlen.