fix: use the correct source host in start_replication.sh

Author: fanyang01

devtools/replica-setup-mysql/start_replication.sh

@@ -20,7 +20,7 @@ fi
 
 # Connect to MySQL and execute the replication configuration commands
 REPLICATION_CMD="CHANGE REPLICATION SOURCE TO \
-  SOURCE_HOST='${SOURCE_HOST_FOR_REPLICA}', \
+  SOURCE_HOST='${SOURCE_HOST}', \
   SOURCE_PORT=${SOURCE_PORT}, \
   SOURCE_USER='${SOURCE_USER}', \
   SOURCE_PASSWORD='${SOURCE_PASSWORD}'"
@@ -42,4 +42,4 @@ if [ $? -ne 0 ]; then
   exit 1
 else
   echo "Replication established successfully."
-fi
+fi