doc: PG 16 relnotes, update xid/subxid searches item

Reported-by: John Naylor

Discussion: https://postgr.es/m/CAFBsxsEPg8L2MmGqavc8JByC=WF_Mnkhn-KKnFPkcqh0hydung@mail.gmail.com

Author: bmomjian

doc/src/sgml/release-16.sgml

@@ -2569,7 +2569,7 @@ Author: John Naylor <john.naylor@postgresql.org>
 
 <listitem>
 <para>
-Allow xid/subxid searches to use vector operations on x86-64 architectures (Nathan Bossart)
+Allow xid/subxid searches to use vector operations (Nathan Bossart)
 </para>
 </listitem>