Bug 1861626 - Install rtoml in the decision task image. r=taskgraph-reviewers,jmaher,releng-reviewers,ahal

Differential Revision: https://phabricator.services.mozilla.com/D273793

Author: marco-c

taskcluster/docker/decision/system-setup.sh

@@ -11,7 +11,7 @@ apt-get install \
     python3-yaml \
     python3-pip
 
-pip install --break-system-packages --disable-pip-version-check --quiet --no-cache-dir orjson==3.10.15
+pip install --break-system-packages --disable-pip-version-check --quiet --no-cache-dir orjson==3.10.15 rtoml==0.13.0
 
 apt-get remove --purge python3-pip
 apt-get autoremove --purge