benchmarks: v6.8.0

- change sample_cluster_1000 benchmark to only sample 500 as there are less than 1000 clusters causing an error
- add cleanup to to_sqlite benchmark, as only the first run is successful, Subsequent runs fail as the exported sqlite db already exists
[skip ci]

Author: jqnatividad

scripts/benchmarks.sh

@@ -42,7 +42,7 @@
 arg_pat="$1"
 
 # the version of this script
-bm_version=6.7.0
+bm_version=6.8.0
 
 # CONFIGURABLE VARIABLES ---------------------------------------
 # change as needed to reflect your environment/workloads