GH-70: Move from hamcrest to assertj in flight-sql (#772)

## What's Changed
Series of PRs to consolidate on using `assertj` in tests as part of
#70.

Author: rtadepalli

flight/flight-sql/pom.xml

@@ -116,16 +116,16 @@ under the License.
       <version>1.13.1</version>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>org.hamcrest</groupId>
-      <artifactId>hamcrest</artifactId>
-      <scope>test</scope>
-    </dependency>
     <dependency>
       <groupId>commons-cli</groupId>
       <artifactId>commons-cli</artifactId>
       <version>1.9.0</version>
       <optional>true</optional>
     </dependency>
+    <dependency>
+      <groupId>org.assertj</groupId>
+      <artifactId>assertj-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>