Switch a few core plugins to the new api
diff --git a/pom.xml b/pom.xml
index 497ccdd..2b88cb7 100644
--- a/pom.xml
+++ b/pom.xml
@@ -284,7 +284,7 @@
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>animal-sniffer-maven-plugin</artifactId>
-        <version>1.20</version>
+        <version>1.21</version>
         <configuration>
           <signature>
             <groupId>org.codehaus.mojo.signature</groupId>