Run maven-source-plugin on jar-no-fork (#176)

*Issue #, if available:*

*Description of changes:* Matches v2
[here](https://github.com/aws/aws-secretsmanager-caching-java/blob/v2/pom.xml#L89)


https://maven.apache.org/plugins/maven-source-plugin/jar-no-fork-mojo.html


By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Author: simonmarty

pom.xml

@@ -85,7 +85,7 @@
                     <execution>
                         <id>attach-sources</id>
                         <goals>
-                            <goal>jar</goal>
+                            <goal>jar-no-fork</goal>
                         </goals>
                     </execution>
                 </executions>