fix(ci): run root install in dependency convergence check

To ensure all BOMs are built and installed in the reactor before
dependency convergence check runs.

TAG=agy
CONV=a43a6fb4-588d-4179-be73-21b28a734018

Author: lqiu96

.kokoro/dashboard.sh

@@ -26,7 +26,7 @@ if [[ "${JOB_TYPE}" == "dashboard-units-check" ]]; then
   mvn test --fail-at-end
 elif [[ "${JOB_TYPE}" == "dependency-convergence-check" ]]; then
   echo -e "\n******************** BUILDING DEPENDENCIES ********************"
-  mvn install -pl java-cloud-bom/libraries-bom,java-cloud-bom/tests/dependency-convergence -am -Pquick-build -DskipTests -Denforcer.skip=true
+  mvn install -T 1C -Pquick-build -DskipTests -Denforcer.skip=true
   cd java-cloud-bom/tests/dependency-convergence/
   echo -e "\n******************** RUNNING DEPENDENCY CONVERGENCE CHECK ********************"
   mvn validate --fail-at-end