fix: Remove duplicate plugin entry

Author: slachiewicz

pom.xml

@@ -564,20 +564,6 @@ limitations under the License.
             </execution>
           </executions>
         </plugin>
-        <plugin>
-          <groupId>org.eclipse.sisu</groupId>
-          <artifactId>sisu-maven-plugin</artifactId>
-          <version>${sisuMavenPluginVersion}</version>
-          <executions>
-            <execution>
-              <id>generate-index</id>
-              <goals>
-                <goal>main-index</goal>
-                <goal>test-index</goal>
-              </goals>
-            </execution>
-          </executions>
-        </plugin>
         <plugin>
           <groupId>com.diffplug.spotless</groupId>
           <artifactId>spotless-maven-plugin</artifactId>