Move PSR-20 docs under accepted; add link to acceptance vote

Author: Jean85

proposed/clock-meta.md renamed to accepted/PSR-20-clock-meta.md

@@ -117,6 +117,7 @@ final class FrozenClock implements \Psr\Clock\ClockInterface
 ## 6. Votes
 
 * [Entrance Vote](https://groups.google.com/g/php-fig/c/hIKqd0an-GI)
+* [Acceptance Vote](https://groups.google.com/g/php-fig/c/4esd62o0QoU)
 
 ## 7. Relevant Links