chore: fix declaration of maven-source-plugin for v3.3.0

[mpeddada1]

The release job is currently failing with:

[INFO] Parent for the Google HTTP Client Library for Java . SUCCESS [  6.038 s]
[INFO] Google HTTP Client Library for Java ................ FAILURE [  8.781 s]
[INFO] Android Platform Extensions to the Google HTTP Client Library for Java. SKIPPED
[INFO] Apache HTTP transport v2 for the Google HTTP Client Library for Java. SKIPPED
[INFO] Shared classes used for testing of artifacts in the Google HTTP Client Library for Java. SKIPPED
[INFO] Google App Engine extensions to the Google HTTP Client Library for Java. SKIPPED
[INFO] GSON extensions to the Google HTTP Client Library for Java. SKIPPED
[INFO] Jackson 2 extensions to the Google HTTP Client Library for Java. SKIPPED
[INFO] Protocol Buffer extensions to the Google HTTP Client Library for Java. SKIPPED
[INFO] XML extensions to the Google HTTP Client Library for Java. SKIPPED
[INFO] Assembly for the Google HTTP Client Library for Java SKIPPED
[INFO] Google APIs Client Library Findbugs custom plugin. . SKIPPED
[INFO] Simple example for the Dailymotion API. ............ SKIPPED
[INFO] Google HTTP Client Library for Java BOM ............ SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  15.888 s
[INFO] Finished at: 2024-01-24T20:33:48Z
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-source-plugin:3.3.0:jar-no-fork (attach-sources) on project google-http-client: Presumably you have configured maven-source-plugn to execute twice times in your build. You have to configure a classifier for at least on of them. -> [Help 1]

This started happening after we included the native-image-shared-config artifact.The parent pom brings in maven-source-plugin:3.3.0 in the release profile` :
https://github.com/googleapis/java-shared-config/blob/28b2c77ddd2078d628cb8f2b16fae8efd0e673a5/native-image-shared-config/pom.xml#L107-L121.

This PR leverages pluginManagement instead of duplicating the setting in all the module poms to address the issue. This is similar to how google-aut-library-java is set up.

<plugin>
        <artifactId>maven-source-plugin</artifactId>
        <executions>
          <execution>
            <id>source-jar</id>
            <phase>compile</phase>
            <goals>
              <goal>jar</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

BEGIN_COMMIT_OVERRIDE
fix: fixing declaration of maven-source-plugin for release job
END_COMMIT_OVERRIDE

[mpeddada1]

The kokoro failure is unrelated to the changes in the PR. See googleapis/java-shared-config#712 (comment) for similar observation in a different repo.