(DOCSP-21998) Removed erroneous curly braces (#890)

Author: JuliaMongo

source/includes/steps-multi-cluster-source.yaml

@@ -125,7 +125,7 @@ content: |
               --version <mongodb-kubernetes-operator-version> \
               --set operator.name=mongodb-enterprise-operator-multi-cluster \
               --set operator.createOperatorServiceAccount=false \
-              --set "multiCluster.clusters={${MDB_CLUSTER_1_FULL_NAME},${MDB_CLUSTER_2_FULL_NAME},${MDB_CLUSTER_3_FULL_NAME}}"
+              --set "multiCluster.clusters=$MDB_CLUSTER_1_FULL_NAME,$MDB_CLUSTER_2_FULL_NAME,$MDB_CLUSTER_3_FULL_NAME"
 ---
 stepnum: 0
 title: "Deploy the MongoDB resource."