Fix improper example of using psql() function in TAP tests documentation.

MasaoFujii · MasaoFujii · commit c1a95425780e · 2016-07-26T21:17:38.000+09:00
In an example of TAP test scripts, there is the test checking whether
the result of the query is expected or not. But, in previous example,
the exit code of psql instead of the query result was checked unexpectedly.

Author: Ildar Musin
diff --git a/src/test/perl/README b/src/test/perl/README
@@ -41,7 +41,7 @@ against them and evaluate the results. For example:
     $node->init;
     $node->start;
 
-    my $ret = $node->psql('postgres', 'SELECT 1');
+    my $ret = $node->safe_psql('postgres', 'SELECT 1');
     is($ret, '1', 'SELECT 1 returns 1');
 
     $node->stop('fast');
