Tests: skip "no headers" test in h2_proxy_cache.t on win32.

Small limit rate doesn't work on this platform which breaks test preconditions.

Author: pluknet

h2_proxy_cache.t

@@ -157,6 +157,9 @@ push @$frames, $_ for @{$s->read(all => [{ sid => $sid }], wait => 0.2)};
 ok(!grep ({ $_->{type} eq "DATA" } @$frames),
 	'proxy cache HEAD buffering off - no body');
 
+SKIP: {
+skip 'win32', 1 if $^O eq 'MSWin32';
+
 # client cancels stream with a cacheable request that was sent to upstream
 # HEADERS should not be produced for the canceled stream
 
@@ -168,6 +171,8 @@ $s->h2_rst($sid, 8);
 $frames = $s->read(all => [{ sid => $sid, fin => 0x4 }], wait => 1.2);
 ok(!(grep { $_->{type} eq "HEADERS" } @$frames), 'no headers');
 
+}
+
 # client closes connection after sending a cacheable request producing alert
 
 $s = Test::Nginx::HTTP2->new();