[3.14] Avoid __file__ in hashlib example (GH-134540) (#134549)

Avoid `__file__` in `hashlib` example (GH-134540)
(cherry picked from commit 9b292ff022)

Co-authored-by: Josh Cannon <joshdcannon@gmail.com>

Doc/library/hashlib.rst

@@ -284,7 +284,7 @@ a file or file-like object.
    Example:
 
       >>> import io, hashlib, hmac
-      >>> with open(hashlib.__file__, "rb") as f:
+      >>> with open("library/hashlib.rst", "rb") as f:
       ...     digest = hashlib.file_digest(f, "sha256")
       ...
       >>> digest.hexdigest()  # doctest: +ELLIPSIS