Bump Placeholder API

gradle.properties

@@ -18,7 +18,7 @@ map_templates_version=0.2.1+1.21.3
 substrate_version=0.2.2+1.20.1
 sgui_version=1.7.2+1.21.2
 sidebar_api_version=0.5.1+1.21.1
-placeholder_api_version=2.5.0+1.21.2
+placeholder_api_version=2.5.1+1.21.3
 map_canvas_api_version=0.5.0+1.21.3
 player_data_api_version=0.7.0+1.21.3
 predicate_api_version=0.6.0+1.21.2