doc: clarify handling of time zones with "time with time zone"

Reported-by: davecramer@postgres.rocks

Discussion: https://postgr.es/m/168451942371.714.9173574930845904336@wrigleys.postgresql.org

Backpatch-through: 11

doc/src/sgml/datatype.sgml

@@ -2028,7 +2028,8 @@ MINUTE TO SECOND
       <literal>America/New_York</literal>. In this case specifying the date
       is required in order to determine whether standard or daylight-savings
       time applies.  The appropriate time zone offset is recorded in the
-      <type>time with time zone</type> value.
+      <type>time with time zone</type> value and is output as stored;
+      it is not adjusted to the active time zone.
      </para>
 
       <table id="datatype-datetime-time-table">