Doc: Clarify generator.close() documentation

Replace 'sends' with 'raises' and clarify that close() is equivalent to throw(GeneratorExit). This makes the documentation clearer and avoids confusion with generator.send().

Author: cdenihan

Doc/reference/expressions.rst

@@ -625,9 +625,10 @@ is already executing raises a :exc:`ValueError` exception.
 
 .. method:: generator.close()
 
-   Sends a :exc:`GeneratorExit` exception to the generator at the point where 
-   the generator function was paused.  If the generator function catches the 
-   exception and returns a
+   Raises a :exc:`GeneratorExit` exception at the point where the generator 
+   function was paused (equivalent to calling ``throw(GeneratorExit)``). 
+   The exception is raised by the yield expression where the generator was paused.
+   If the generator function catches the exception and returns a
    value, this value is returned from :meth:`close`.  If the generator function
    is already closed, or raises :exc:`GeneratorExit` (by not catching the
    exception), :meth:`close` returns :const:`None`.  If the generator yields a