Fix out-of-date version reference, grammar.

Time appears to be passing fast.
Reported-By: Peter Geoghegan <pg@bowt.ie>

src/backend/access/nbtree/README

@@ -412,7 +412,7 @@ the cost of walking down the tree in such common cases.
 
 The optimization works on the assumption that there can only be one
 non-ignorable leaf rightmost page, and so not even a visible-to-everyone
-style interlock required.  We cannot fail to detect that our hint was
+style interlock is required.  We cannot fail to detect that our hint was
 invalidated, because there can only be one such page in the B-Tree at
 any time. It's possible that the page will be deleted and recycled
 without a backend's cached page also being detected as invalidated, but

src/backend/access/transam/README

@@ -318,7 +318,7 @@ XID less than this could be about to appear in the ProcArray, because of the
 XidGenLock interlock discussed above.)
 
 As GetSnapshotData is performance critical, it does not perform an accurate
-oldest-xmin calculation (it used to, until v13). The contents of a snapshot
+oldest-xmin calculation (it used to, until v14). The contents of a snapshot
 only depend on the xids of other backends, not their xmin. As backend's xmin
 changes much more often than its xid, having GetSnapshotData look at xmins
 can lead to a lot of unnecessary cacheline ping-pong.  Instead