Add entry for upper and lower template helpers to changelog (#3262)

Author: shreyas-goenka

NEXT_CHANGELOG.md

@@ -14,5 +14,6 @@
 ### Bundles
 
  * Jobs that use cluster policy default values for their cluster configuration now correctly update those defaults on every deployment ([#3255](https://github.com/databricks/cli/pull/3255)).
+ * Add upper and lower helper methods for bundle templates ([#3242](https://github.com/databricks/cli/pull/3242))
 
 ### API Changes