Update Doc/library/_thread.rst

Co-authored-by: Furkan Onder <furkanonder@protonmail.com>

Author: yuce

Doc/library/_thread.rst

@@ -127,7 +127,7 @@ This module defines the following constants and functions:
    .. versionchanged:: 3.13
       Added support for GNU/kFreeBSD.
 
-   .. versionchanged:: 3.15
+   .. versionchanged:: next
       Added support for Solaris.
 
 .. function:: stack_size([size])