metadata: remove WP_METADATA_FEATURES_STANDARD and fix copyright years

lib/wp/metadata.c

 /* WirePlumber
  *
- * Copyright © 2019-2020 Collabora Ltd.
+ * Copyright © 2020 Collabora Ltd.
  *    @author Raghavendra Rao <raghavendra.rao@collabora.com>
  *
  * SPDX-License-Identifier: MIT

lib/wp/metadata.h

 /* WirePlumber
  *
- * Copyright © 2019 Collabora Ltd.
+ * Copyright © 2020 Collabora Ltd.
  *    @author Raghavendra Rao <raghavendra.rao@collabora.com>
  *
  * SPDX-License-Identifier: MIT
@@ -13,9 +13,6 @@
 
 G_BEGIN_DECLS
 
-#define WP_METADATA_FEATURES_STANDARD \
-    (WP_PROXY_FEATURES_STANDARD)
-
 /**
  * WP_TYPE_METADATA:
  *