Hi dilpreet kaur
Answering to the question I guess upgrading the Databricks Runtime version does not necessarily require changing the instance type of your cluster, so it's not required to upgrade the instance type while upgrading runtime version.
you should consider the instance type in the context of your workload requirements and performance expectations. If you have specific performance or resource requirements, you might decide to adjust the instance type accordingly.
If this helps kindly accept the answer thanks much.