testcases: let i3test.pm export $x, adapt testcases

testcases/t/147-regress-floatingmove.t

@@ -4,16 +4,8 @@
 # Regression test for moving a con outside of a floating con when there are no
 # tiling cons on a workspace
 #
-use X11::XCB qw(:all);
-use Time::HiRes qw(sleep);
 use i3test;
 
-BEGIN {
-    use_ok('X11::XCB::Window');
-}
-
-my $x = X11::XCB::Connection->new;
-
 my $tmp = fresh_workspace;
 
 my $left = open_window($x);