fix: revert maven-source-plugin to 3.2.1 (#297)

* update Maven version on Kokoro cluster to fix release pipeline

* fix: update Maven version on Kokoro cluster to fix release pipeline

* fix: update the dependecy version

* fix: revert maven-javadoc-plugin to 3.2.1

Author: dixuswe

functions-framework-api/pom.xml

@@ -73,7 +73,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-source-plugin</artifactId>
-        <version>3.3.1</version>
+        <version>3.2.1</version>
         <executions>
           <execution>
             <id>attach-sources</id>
@@ -151,7 +151,7 @@
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-source-plugin</artifactId>
-            <version>3.6.0</version>
+            <version>3.2.1</version>
             <executions>
               <execution>
                 <id>attach-sources</id>