DOC: update nep50 status to move relevant doc to Finished NEPs section

Author: amedinaaa

doc/neps/nep-0050-scalar-promotion.rst

@@ -4,7 +4,7 @@
 NEP 50 — Promotion rules for Python scalars
 ===========================================
 :Author: Sebastian Berg
-:Status: Draft
+:Status: Final
 :Type: Standards Track
 :Created: 2021-05-25