doc: update year

juzhiyuan · membphis · commit 218848a25c80 · 2020-02-15T10:29:17.000+08:00
diff --git a/NOTICE b/NOTICE
@@ -1,5 +1,5 @@
 Apache APISIX Dashboard (incubating)
-Copyright 2019 The Apache Software Foundation
+Copyright 2020 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).
