bpo-33885: Replace "hook function" with "callable" (GH-7765)

Doc/library/urllib.request.rst

@@ -1339,9 +1339,9 @@ some point in the future.
 
    The second argument, if present, specifies the file location to copy to (if
    absent, the location will be a tempfile with a generated name). The third
-   argument, if present, is a hook function that will be called once on
+   argument, if present, is a callable that will be called once on
    establishment of the network connection and once after each block read
-   thereafter.  The hook will be passed three arguments; a count of blocks
+   thereafter.  The callable will be passed three arguments; a count of blocks
    transferred so far, a block size in bytes, and the total size of the file.  The
    third argument may be ``-1`` on older FTP servers which do not return a file
    size in response to a retrieval request.