bpo-38605: Update __future__ module doc as annotations is now "mandatory in 3.11" (GH-25602)

Author: gousaiyang

Doc/library/__future__.rst

@@ -90,7 +90,7 @@ language using this mechanism:
 | generator_stop | 3.5.0b1 | 3.7 | :pep:`479`: |
 | | | | *StopIteration handling inside generators* |
 +------------------+-------------+--------------+---------------------------------------------+
-| annotations | 3.7.0b1 | 3.10 | :pep:`563`: |
+| annotations | 3.7.0b1 | 3.11 | :pep:`563`: |
 | | | | *Postponed evaluation of annotations* |
 +------------------+-------------+--------------+---------------------------------------------+