Revert "remove datasets from gitignore"

This reverts commit 17aa2c0.

Author: gforsyth

.gitignore

@@ -81,7 +81,7 @@ ivf_flat_index
 ivf_pq_index
 
 # cuvs_bench
-#datasets/
+datasets/
 !python/cuvs_bench/cuvs_bench/config/datasets/datasets.yaml
 /*.json