doc: fix javadoc error

Javadoc was exiting with the following error on JDK 13

  error: heading used out of sequence: <H2>, compared to implicit
  preceding heading: <H0>

Flag added to suppress the error.

Author: dmaccormack

module/pom.xml

@@ -178,7 +178,7 @@
             <javadocVersion>${jdk.version}</javadocVersion>
             <source>${jdk.version}</source>
 
-            <doclint>all,-missing</doclint>
+            <doclint>all,-missing,-accessibility</doclint>
             <!--
               Ideally I'd simply link to javadoc.io for everything here via
               <links>...</links>. However, there are a number of pitfalls when