Doc fixes for MERGE statement

In commit 3d895bc I introduced a bogus semicolon mid-statement by
careless cut-n-paste; move it.  This had already been reported by Justin
Pryzby.

Also, change the styling a bit by avoiding names in CamelCase.  This is
more consistent with the style we use elsewhere.

Backpatch to 15.

Author: Vitaly Burovoy <vitaly.burovoy@gmail.com>
Reviewed-by: Vik Fearing <vik@postgresfriends.org>
Discussion: https://postgr.es/m/9afe5766-5a61-7860-598c-136867fad065@gmail.com
Discussion: https://postgr.es/m/20220819133016.GV26426@telsasoft.com

Author: alvherre

doc/src/sgml/ref/merge.sgml

@@ -554,18 +554,18 @@ MERGE <replaceable class="parameter">total_count</replaceable>
   <title>Examples</title>
 
   <para>
-   Perform maintenance on <literal>CustomerAccounts</literal> based
-   upon new <literal>Transactions</literal>.
+   Perform maintenance on <literal>customer_accounts</literal> based
+   upon new <literal>recent_transactions</literal>.
 
 <programlisting>
-MERGE INTO CustomerAccount CA
-USING RecentTransactions T
-ON T.CustomerId = CA.CustomerId
+MERGE INTO customer_account ca
+USING recent_transactions t
+ON t.customer_id = ca.customer_id
 WHEN MATCHED THEN
-  UPDATE SET Balance = Balance + TransactionValue
+  UPDATE SET balance = balance + transaction_value
 WHEN NOT MATCHED THEN
-  INSERT (CustomerId, Balance)
-  VALUES (T.CustomerId, T.TransactionValue);
+  INSERT (customer_id, balance)
+  VALUES (t.customer_id, t.transaction_value);
 </programlisting>
   </para>
 
@@ -575,14 +575,14 @@ WHEN NOT MATCHED THEN
    during execution.
 
 <programlisting>
-MERGE INTO CustomerAccount CA
-USING (Select CustomerId, TransactionValue From RecentTransactions) AS T
-ON T.CustomerId = CA.CustomerId
+MERGE INTO customer_account ca
+USING (SELECT customer_id, transaction_value FROM recent_transactions) AS t
+ON t.customer_id = ca.customer_id
 WHEN MATCHED THEN
-  UPDATE SET Balance = Balance + TransactionValue;
+  UPDATE SET balance = balance + transaction_value
 WHEN NOT MATCHED THEN
-  INSERT (CustomerId, Balance)
-  VALUES (T.CustomerId, T.TransactionValue)
+  INSERT (customer_id, balance)
+  VALUES (t.customer_id, t.transaction_value);
 </programlisting>
   </para>