Revert "Silence compiler warning"

This reverts commit 9dc12258.

As committed, statement sampling used the existing duration threshold
(log_min_duration_statement) when decide which statements to sample.
The issue is that even the longest statements are subject to sampling,
and so may not end up logged. An improvement was proposed, introducing
a second duration threshold, but it would not be backwards compatible.
So we've decided to revert this feature - the separate threshold should
be part of the feature itself.

Discussion: https://postgr.es/m/CAFj8pRDS8tQ3Wviw9%3DAvODyUciPSrGeMhJi_WPE%2BEB8%2B4gLL-Q%40mail.gmail.com

src/backend/tcop/postgres.c

@@ -2256,14 +2256,13 @@ check_log_duration(char *msec_str, bool was_logged)
 
 		/*
 		 * Do not log if log_statement_sample_rate = 0. Log a sample if
-		 * log_statement_sample_rate <= 1 and avoid unnecessary random() call
-		 * if log_statement_sample_rate = 1.  But don't compute any of this
-		 * unless needed.
+		 * log_statement_sample_rate <= 1 and avoid unecessary random() call
+		 * if log_statement_sample_rate = 1.
 		 */
-		in_sample = exceeded &&
-			log_statement_sample_rate != 0 &&
-			(log_statement_sample_rate == 1 ||
-			 random() <= log_statement_sample_rate * MAX_RANDOM_VALUE);
+		if (exceeded)
+			in_sample = log_statement_sample_rate != 0 &&
+				(log_statement_sample_rate == 1 ||
+				 random() <= log_statement_sample_rate * MAX_RANDOM_VALUE);
 
 		if ((exceeded && in_sample) || log_duration || xact_is_sampled)
 		{