fix javadoc configuration

Crim · Crim · commit 4f9b5d745e7a · 2020-07-30T10:53:36.000+09:00
diff --git a/pom.xml b/pom.xml
@@ -345,6 +345,9 @@
                                 <goals>
                                     <goal>jar</goal>
                                 </goals>
+                                <configuration>
+                                    <source>8</source>
+                                </configuration>
                             </execution>
                         </executions>
                     </plugin>
