node: Expose .cancel at the node layer

src/node.zig

@@ -147,6 +147,10 @@ pub fn despawn(self: *Node, id: TaskID) void {
     self.scheduler.despawnNested(id);
 }
 
+pub fn cancel(self: *Node, id: TaskID) !void {
+    try self.scheduler.cancel(id);
+}
+
 pub fn wait(self: *Node, ids: []const TaskID) !TaskID {
     return self.scheduler.wait(ids);
 }