docs(runbook): use a real repo in job/build examples

Replace the non-existent myrepo.git placeholder (which fails with
"repository not found") with this repo's URL and a harmless
`echo build-ok` build command, so §3 and §4.3 run as pasted.

docs/RUNBOOK-PhaseC.md

@@ -184,10 +184,10 @@ ci job \
   --job-id manual-$(date +%s) \
   --template-path /var/lib/ci/templates/LinuxBuild2404/LinuxBuild2404.vmx \
   --snapshot-name BaseClean-Linux \
-  --repo-url https://gitea.emulab.it/Simone/myrepo.git \
+  --repo-url https://gitea.emulab.it/Simone/local-ci-cd-system.git \
   --branch main \
   --guest-os linux \
-  --build-command "make all" \
+  --build-command "echo build-ok" \
   --use-git-clone
 ```
 
@@ -252,8 +252,8 @@ ci build run \
   --ip-address "$IP" \
   --guest-os linux \
   --ssh-user ci_build --ssh-key-path /var/lib/ci/keys/ci_linux \
-  --clone-url https://gitea.emulab.it/Simone/myrepo.git --clone-branch main \
-  --build-command "make all" \
+  --clone-url https://gitea.emulab.it/Simone/local-ci-cd-system.git --clone-branch main \
+  --build-command "echo build-ok" \
   --guest-artifact-source dist
 ```