containerized-rpmbuild: fix typo in installing packages string (#8704)

Change #7982 introduced a typo in the variable name we use to print which extra packages containerized-rpmbuild will install. The correct packages are installed, but the string informing the user what's being installed doesn't print the extra packages.

This change fixes that.

toolkit/scripts/containerized-build/resources/azl.Dockerfile

@@ -25,5 +25,5 @@ RUN if [[ "${mode}" == "build" ]]; then echo "cd /usr/src/azl || { echo \"ERROR:
 RUN if [[ "${mode}" == "test" ]]; then echo "cd /mnt || { echo \"ERROR: Could not change directory to /mnt \"; exit 1; }"  >> /root/.bashrc; fi
 
 # Install packages from bashrc so we can use the previously setup tdnf defaults.
-RUN echo "echo installing packages vim git ${coextra_packages}" >> /root/.bashrc && \
+RUN echo "echo installing packages vim git ${extra_packages}" >> /root/.bashrc && \
     echo "tdnf install -qy vim git ${extra_packages}" >> /root/.bashrc