HADOOP-16253. Update AssertJ to 3.12.2.

Author: tasanuma

hadoop-project/pom.xml

@@ -167,6 +167,7 @@
     <junit.jupiter.version>5.3.1</junit.jupiter.version>
     <junit.vintage.version>5.3.1</junit.vintage.version>
     <junit.platform.version>1.3.1</junit.platform.version>
+    <assertj.version>3.12.2</assertj.version>
     <jline.version>3.9.0</jline.version>
     <powermock.version>1.5.6</powermock.version>
     <solr.version>7.7.0</solr.version>
@@ -1514,7 +1515,7 @@
         <dependency>
           <groupId>org.assertj</groupId>
           <artifactId>assertj-core</artifactId>
-          <version>3.8.0</version>
+          <version>${assertj.version}</version>
           <scope>test</scope>
         </dependency>
       <dependency>

hadoop-tools/hadoop-fs2img/pom.xml

@@ -69,7 +69,6 @@
     <dependency>
       <groupId>org.assertj</groupId>
       <artifactId>assertj-core</artifactId>
-      <version>3.8.0</version>
       <scope>test</scope>
     </dependency>
   </dependencies>