tests: make cmp_float a real test instruction

testcases/lib/i3test.pm

@@ -33,7 +33,6 @@ our @EXPORT = qw(
     open_floating_window
     get_dock_clients
     cmd
-    cmp_float
     sync_with_i3
     does_i3_live
     exit_gracefully
@@ -566,13 +565,7 @@ sub launch_with_config {
     return $i3_pid;
 }
 
-# compares two floats and return true if they differ less
-# then 1e-6
-sub cmp_float {
-  my ($a, $b) = @_;
 
-  return abs($a - $b) < 1e-6;
-}
 
 package i3test::X11;
 use parent 'X11::XCB::Connection';