build: downgrade maven-sources-plugin from 3.3.0 to 3.2.1

The new version of the plugin caused build failure because of duplicate configurations.

Before fixing the root cause, downgrade to the old version.

pom.xml

@@ -45,12 +45,6 @@
         <version>1.5.2</version>
       </dependency>
 
-      <dependency>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-source-plugin</artifactId>
-        <version>3.2.1</version>
-      </dependency>
-
     </dependencies>
   </dependencyManagement>
 
@@ -91,6 +85,17 @@
   </dependencies>
 
   <build>
+
+    <pluginManagement>
+      <plugins>
+        <plugin>
+          <groupId>org.apache.maven.plugins</groupId>
+          <artifactId>maven-source-plugin</artifactId>
+          <version>3.2.1</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+
     <plugins>
       <plugin>
         <groupId>org.springframework.boot</groupId>