Include ni-grpc-device.conf.yml and ni-grpc-device.caps.yml in Linux RT tarball

[texasaggie97]

What does this Pull Request accomplish?

Adds ni-grpc-device.conf.yml and ni-grpc-device.caps.yml to the "Tar Server Build Files"
step in build_nilrt.yml. Both files are now included in the
ni-grpc-device-server-ni-linux-rt-x64.tar.gz artifact alongside the existing
server_config.json and server_capabilities.json.

Why should this Pull Request be merged?

These TLS config files were added in a previous PR but were missing from the Linux RT
tarball. The CMake build already copies both files from source/config/ to the binary
output directory for all targets (including the NILRT cross-compile), so they are present
in $GITHUB_WORKSPACE/build/ at packaging time — they simply weren't included in the
tar command.

Without this fix, users installing from the Linux RT tarball would not receive the default
TLS configuration files needed by the server.

What testing has been done?

This change is a one-line workflow addition to an existing tar command. Coverage is
provided by the CI pipeline: the build_nilrt.yml workflow will produce the tarball and
the artifact contents can be verified to include both .yml files.