Add missing artifact required for the Javadoc task

See gh-10696

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

@@ -812,6 +812,11 @@
 			<artifactId>spring-restdocs-mockmvc</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.restdocs</groupId>
+			<artifactId>spring-restdocs-webtestclient</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.security</groupId>
 			<artifactId>spring-security-data</artifactId>