Don't VALGRIND_PRINTF() each query string.

Doing so was helpful for some Valgrind usage and distracting for other
usage.  One can achieve the same effect by changing log_statement and
pointing both PostgreSQL and Valgrind logging to stderr.

Per gripe from Andres Freund.

src/backend/tcop/postgres.c

@@ -69,7 +69,6 @@
 #include "tcop/tcopprot.h"
 #include "tcop/utility.h"
 #include "utils/lsyscache.h"
-#include "utils/memdebug.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
 #include "utils/snapmgr.h"
@@ -847,10 +846,6 @@ exec_simple_query(const char *query_string)
 
 	TRACE_POSTGRESQL_QUERY_START(query_string);
 
-#ifdef USE_VALGRIND
-	VALGRIND_PRINTF("statement: %s\n", query_string);
-#endif
-
 	/*
 	 * We use save_log_statement_stats so ShowUsage doesn't report incorrect
 	 * results because ResetUsage wasn't called.