update to Maven 3.8.4, also build with Java 17

Author: stefanseifert

.github/workflows/maven-build.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest ]
-        java: [8, 11]
+        java: [8, 11, 17]
 
     steps:
       # Check out Git repository

.mvn/wrapper/maven-wrapper.properties

@@ -1,2 +1,2 @@
-distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.8.1/apache-maven-3.8.1-bin.zip
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.8.4/apache-maven-3.8.4-bin.zip
 wrapperUrl=https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar