chore: update maven-javadoc-plugin to 3.1.1

Changelogs:
- https://mail-archives.apache.org/mod_mbox/maven-announce/201903.mbox/%3C6064d830-474c-4b43-afef-99502c3a305a%40getmailbird.com%3E
- https://mail-archives.apache.org/mod_mbox/maven-announce/201907.mbox/%3CCAPoyBqS_jmC_T%2Bg2jet6VoP-_CKFFtEZ-r_-EMvST%3D_RonWeCg%40mail.gmail.com%3E

Fix #1178

Author: php-coder

pom.xml

@@ -556,7 +556,7 @@
 		-->
 		<java.version>1.8</java.version>
 
-		<javadoc.plugin.version>3.0.1</javadoc.plugin.version>
+		<javadoc.plugin.version>3.1.1</javadoc.plugin.version>
 		<javassist.version>3.21.0-GA</javassist.version>
 
 		<!-- Redefine default value from spring-boot-dependencies -->