Simplify TAP test structure to align with upstream (#169)

postgres/postgres@549ec20 moved to using "done_testing()" from
the Perl testing framework, which removed the need to include test
counts.

test/t/001_wal.pl

@@ -5,7 +5,7 @@ use strict;
 use warnings;
 use PostgresNode;
 use TestLib;
-use Test::More tests => 31;
+use Test::More;
 
 my $dim = 32;
 
@@ -95,3 +95,5 @@ for my $i (1 .. 10)
 	);
 	test_index_replay("insert $i");
 }
+
+done_testing();