Fix the dependency dubbo-config-spring missing in dubbo-spring-boot.(#14947)

Author: lanxi0

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

@@ -52,6 +52,12 @@
       <version>${project.version}</version>
       <optional>true</optional>
     </dependency>
+    <dependency>
+      <groupId>org.apache.dubbo</groupId>
+      <artifactId>dubbo-config-spring</artifactId>
+      <version>${project.version}</version>
+      <optional>true</optional>
+    </dependency>
 
     <!-- Test Dependencies -->
     <dependency>