Synchronize doc/ copies of src/test/examples/.

This is mostly cosmetic, but it might fix build failures, on some
platform, when copying from the documentation.

Back-patch to 9.3 (all supported versions).

src/test/examples/testlibpq2.sql

@@ -3,4 +3,4 @@ CREATE TABLE TBL1 (i int4);
 CREATE TABLE TBL2 (i int4);
 
 CREATE RULE r1 AS ON INSERT TO TBL1 DO
-(INSERT INTO TBL2 VALUES (new.i); NOTIFY TBL2);
+  (INSERT INTO TBL2 VALUES (new.i); NOTIFY TBL2);