Doc: clarify description for pg_constraint.convalidated.

Jimmy Angelakos

Discussion: https://postgr.es/m/CABgVKCW_zPnvFXn24FTF0299_yU6+1p6JRUc0xpiZFWEXH1_jg@mail.gmail.com

doc/src/sgml/catalogs.sgml

@@ -2508,7 +2508,7 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para>
       <para>
        Has the constraint been validated?
-       Currently, can only be false for foreign keys and CHECK constraints
+       Currently, can be false only for foreign keys and CHECK constraints
       </para></entry>
      </row>