ci: upgrade maven to version 3.8.9

Previous version is no longer available at [1].

[1]: https://dlcdn.apache.org/maven/maven-3/

Author: darrachequesne

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
 
       - name: Install Maven 3.8.x (instead of 3.9.x)
         run: |
-          MAVEN_VERSION=3.8.8
+          MAVEN_VERSION=3.8.9
           wget https://downloads.apache.org/maven/maven-3/$MAVEN_VERSION/binaries/apache-maven-$MAVEN_VERSION-bin.tar.gz
           tar xzvf apache-maven-$MAVEN_VERSION-bin.tar.gz
           sudo mv apache-maven-$MAVEN_VERSION /opt/maven