Up the busy-timeout for multiple connections test

This started failing with 'database is locked' at some point
for some systems.  It will only slow down the tests in those cases
where it was going to fail anyway.

Fixes #136

t/43-sqlite-threads.t

@@ -24,6 +24,7 @@ my $dbh = DBIish.connect("SQLite", :$database);
 END try $dbh.dispose;
 $dbh.do('CREATE TABLE nom ( name varchar(50) )');
 
+
 # Check that it is possible to work with the database from multiple threads
 # at once with a single connection option. This works in SQLite's serialized
 # mode, which is the default.
@@ -59,7 +60,7 @@ subtest 'Statements across threads on one connection' => {
 subtest 'Multiple connections, one per thread' => {
     my @inserters = do for ^5 -> $thread {
         start {
-            my $dbht = DBIish.connect("SQLite", :$database);
+            my $dbht = DBIish.connect("SQLite", :$database, busy-timeout => 30000);
             for ^100 {
                 my $sth = $dbht.prepare(q:to/STATEMENT/);
                     INSERT INTO nom (name)