Update install schema command (#92)

Update install schema command in README

Co-authored-by: Alex Stanfield <13949480+chaptersix@users.noreply.github.com>

Author: phuongdnguyen

extensibility/metrics-handler/README.md

@@ -7,7 +7,7 @@ This sample shows how to inject a custom metrics handler.
 as described in the 
 [contribution guide](https://github.com/temporalio/temporal/blob/master/CONTRIBUTING.md#runing-server-locally).
 
-2. Create the database schema by running `make install-schema`.
+2. Create the database schema by running `make install-schema-cass-es`.
 
 3. Start Temporal by running `go run metrics-reporter/server/main.go`.