Revert r87821 which moved the source link to the wrong section (from the module…

Revert r87821 which moved the source link to the wrong section (from the module intro covering the module to a section on thread imports).

Doc/library/threading.rst

@@ -28,6 +28,11 @@ The :mod:`dummy_threading` module is provided for situations where
    However, threading is still an appropriate model if you want to run
    multiple I/O-bound tasks simultaneously.
 
+.. seealso::
+
+   Latest version of the :source:`threading module Python source code
+   <Lib/threading.py>`
+
 
 This module defines the following functions and objects:
 
@@ -965,9 +970,3 @@ provided:
   abide by this restriction will lead to intermittent exceptions and
   crashes during interpreter shutdown (as the late imports attempt to
   access machinery which is no longer in a valid state).
-
-
-.. seealso::
-
-   Latest version of the :source:`threading module Python source code
-   <Lib/threading.py>`