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.
diff --git a/Misc/NEWS b/Misc/NEWS
index 4012c96..e47766a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -21,6 +21,8 @@
 Library
 -------
 
+- Rename adjusted attribute to adjustable in time.get_clock_info() result.
+
 - Issue #3518: Remove references to non-existent BaseManager.from_address()
   method.