Add missing repo to enable building with -Ddremio.oss-only=true

[pvallone]

The README mentions here that Dremio can be built with only OSS dependencies by specifying the -Ddremio.oss-only=true flag. Currently, this fails with the error below because com.dremio.data:dremio-tpch-sample-data can't be pulled from the dremio-public repo. This PR makes the dremio-free repo accessible to the build. It seems like an alternative (and perhaps preferable) solution would be to add com.dremio.data:dremio-tpch-sample-data to the dremio-public repo, but I'm guessing only the Dremio team has the ability to add things to that repo.

Without this change, the build fails with the error below when running this command: mvn clean install -DskipTests -Ddremio.oss-only=true

[ERROR] Failed to execute goal on project dremio-sabot-kernel: Could not resolve dependencies for project com.dremio.sabot:dremio-sabot-kernel:jar:21.2.0-202205262146080444-038d6d1b: Could not find artifact com.dremio.data:dremio-tpch-sample-data:jar:1.0.0 in dremio-public (https://maven.dremio.com/public/) -> [Help 1]

There are several issues open about this build failure. Here's one such example.

[pvallone]

I did notice this bit of code from this part of pom.xml. That suggests that the dremio-free repo is not meant to be included when the dremio.oss-only flag is set. This suggests it would be preferable to fix the build by adding com.dremio.data:dremio-tpch-sample-data to dremio-public.

      <id>community-build</id>
      <activation>
        <property>
          <name>dremio.oss-only</name>
          <value>!true</value>
        </property>
      </activation>
      <repositories>
        <repository>
          <id>dremio-free</id>
          <url>https://maven.dremio.com/free/</url>
        </repository>
      </repositories>