fix(java): adjust children module version of pom to avoid warning

### Describe the enhancement requested

When running maven-projects, there are warning like:
```bash
[WARNING]
[WARNING] Some problems were encountered while building the effective model for org.apache.graphar:graphar-info:jar:0.12.0-SNAPSHOT
[WARNING] 'version' contains an expression but should be a constant. @ org.apache.graphar:graphar-info:${graphar.version}, /home/john/graphar/incubator-graphar/maven-projects/info/pom.xml, line 37, column 14
[WARNING] 'version' contains an expression but should be a constant. @ org.apache.graphar:graphar-root:${graphar.version}, /home/john/graphar/incubator-graphar/maven-projects/pom.xml, line 32, column 14
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
```

should remove version property, since child module will **automatically inherit** the version from the parent, and add comment to notice that.

refer: https://stackoverflow.com/questions/1981151/warning-on-using-project-parent-version-as-the-version-of-a-module-in-maven-3


### Component(s)

Java, Spark

Inspect maven-projects/pom.xml and maven-projects/info/pom.xml, especially the version entries identified in the warning. Run Maven on the projects first to reproduce the warnings, then remove the child version property, add the requested explanatory comment, and rerun the build to confirm the warnings are gone.

Written by the indexing model from the issue text.