Fix maven links.

[ci skip]

Change-Id: Ibefbdf441d932c5751235c635244450d7cbacc53

protoc-artifacts/Dockerfile

@@ -21,7 +21,7 @@ ENV JAVA_HOME /var/local/jdk1.8.0_45
 ENV PATH $JAVA_HOME/bin:$PATH
 
 # Install Maven
-RUN wget -q http://apache.cs.utah.edu/maven/maven-3/3.3.3/binaries/apache-maven-3.3.3-bin.tar.gz -O - | \
+RUN wget -q http://apache.cs.utah.edu/maven/maven-3/3.3.9/binaries/apache-maven-3.3.9-bin.tar.gz -O - | \
     tar xz -C /var/local
 ENV PATH /var/local/apache-maven-3.3.3/bin:$PATH