Update relay tutorial

[mohamedsayed18]

🦟 Bug fix

While reviewing relay tutorial #2112. I found that it needs some updates.

Summary

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

[mohamedsayed18]

The Dockerfile fails as some of the following libraries not released yet

    libgz-cmake5-dev \
    libgz-math9-dev \
    libgz-msgs12-dev \
    libgz-utils4-cli-dev \
    libgflags-dev \

Should I update it to the old version, or we will no longer use major version

[caguero]

The Dockerfile fails as some of the following libraries not released yet

    libgz-cmake5-dev \
    libgz-math9-dev \
    libgz-msgs12-dev \
    libgz-utils4-cli-dev \
    libgflags-dev \

Should I update it to the old version, or we will no longer use major version

These packages are available in the prerelease package repository. Could you add this entry after the line where we add the stable repository?

&& /bin/sh -c 'echo "deb [trusted=yes] http://packages.osrfoundation.org/gazebo/ubuntu-prerelease `lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-prerelease.list' \

[caguero]

Thanks! Looks great to me. Just waiting to enable the prerelease repository.

[mohamedsayed18]

Thanks! Looks great to me. Just waiting to enable the prerelease repository.

Prelease enabled