PEP 418: Rename adjusted attribute to adjustable in time.get_clock_info() result

Fix also its value on Windows and Linux according to its documentation:
"adjustable" indicates if the clock *can be* adjusted, not if it is or was
adjusted.

In most cases, it is not possible to indicate if a clock is or was adjusted.

Doc/library/time.rst

@@ -255,8 +255,8 @@ The module defines the following functions and data items:
 
    The result has the following attributes:
 
-   - *adjusted*: ``True`` if the clock can be adjusted (e.g. by a NTP daemon),
-     ``False`` otherwise
+   - *adjustable*: ``True`` if the clock can be changed automatically (e.g. by
+     a NTP daemon) or manually by the system administrator, ``False`` otherwise
    - *implementation*: The name of the underlying C function used to get
      the clock value
    - *monotonic*: ``True`` if the clock cannot go backward,