Remove unused include in sequenced_worker_pool.h

net/ssl/ssl_platform_key_util.h

Index: net/ssl/ssl_platform_key_util.h
diff --git a/net/ssl/ssl_platform_key_util.h b/net/ssl/ssl_platform_key_util.h
index 5fda648fba55a00b6bd1393c61d589c01019cc8d..31ee09101e17ec12dcdc4ab3124d78b6c0ad388f 100644
--- a/net/ssl/ssl_platform_key_util.h
+++ b/net/ssl/ssl_platform_key_util.h
@@ -8,13 +8,10 @@
 #include <stddef.h>
 
 #include "base/memory/ref_counted.h"
+#include "base/single_thread_task_runner.h"
 #include "net/base/net_export.h"
 #include "net/ssl/ssl_private_key.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
 namespace net {
 
 class X509Certificate;