Downgrade maven-shade-plugin to 3.2.4 for arrow-vector only

There are issues looking up FlatBuffers in the arrow-tools
tests if arrow-vector gets shaded with a newer version up to
at least 3.5.1.

java/vector/pom.xml

@@ -174,6 +174,13 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-shade-plugin</artifactId>
+        <!--
+          Downgrade maven-shade-plugin specifically for this module.
+          Using a newer version up to at least 3.5.1 will cause
+          issues in the arrow-tools tests looking up FlatBuffer
+          dependencies.
+         -->
+        <version>3.2.4</version>
         <executions>
           <execution>
             <phase>package</phase>