Add dependency management for xmlunit-assertj and xmlunit-placeholders

Closes gh-15532

spring-boot-project/spring-boot-dependencies/pom.xml

@@ -3012,6 +3012,11 @@
 				<artifactId>sqlite-jdbc</artifactId>
 				<version>${sqlite-jdbc.version}</version>
 			</dependency>
+			<dependency>
+				<groupId>org.xmlunit</groupId>
+				<artifactId>xmlunit-assertj</artifactId>
+				<version>${xmlunit2.version}</version>
+			</dependency>
 			<dependency>
 				<groupId>org.xmlunit</groupId>
 				<artifactId>xmlunit-core</artifactId>
@@ -3027,6 +3032,11 @@
 				<artifactId>xmlunit-matchers</artifactId>
 				<version>${xmlunit2.version}</version>
 			</dependency>
+			<dependency>
+				<groupId>org.xmlunit</groupId>
+				<artifactId>xmlunit-placeholders</artifactId>
+				<version>${xmlunit2.version}</version>
+			</dependency>
 			<dependency>
 				<groupId>org.yaml</groupId>
 				<artifactId>snakeyaml</artifactId>