[io grant] Use bin IO::Handle to test its .Supply

As part of the IO Action Plan it was deemed the test was erroneous.

.Supply was made to respect the handle's mode[^1], which requires
the test to be amended.

[1] rakudo/rakudo@184d499961

Author: zoffixznet

S16-io/supply.t

@@ -27,8 +27,8 @@ for ThreadPoolScheduler.new, CurrentThreadScheduler -> $*SCHEDULER {
     }
 
     {
-        my $handle = open($filename);
-        tap-ok $handle.Supply(:size(1),:bin),
+        my $handle = open($filename, :bin);
+        tap-ok $handle.Supply(:size(1)),
           [<a b c d e>.map: { Buf[uint8].new(ord $_) }],
           :!live,
           "we can get bytes from a supply";