docs(cms): correct CMS.MERGE requirements (#4188)

probabilistic.go

@@ -971,8 +971,8 @@ func isValidCMSCellSize(cellSize int64) bool {
 }
 
 // CMSMerge merges multiple Count-Min Sketch filters into a single filter.
-// The destination filter must not exist and will be created with the dimensions of the first source filter.
-// The number of items in each source filter must be equal.
+// The destination filter must already be initialized and all filters must have
+// the same width and depth. The filters do not need to contain the same number of items.
 // Returns OK on success or an error if the filters could not be merged.
 // For more information - https://redis.io/commands/cms.merge/
 func (c cmdable) CMSMerge(ctx context.Context, destKey string, sourceKeys ...string) *StatusCmd {
@@ -986,8 +986,8 @@ func (c cmdable) CMSMerge(ctx context.Context, destKey string, sourceKeys ...str
 }
 
 // CMSMergeWithWeight merges multiple Count-Min Sketch filters into a single filter with weights for each source filter.
-// The destination filter must not exist and will be created with the dimensions of the first source filter.
-// The number of items in each source filter must be equal.
+// The destination filter must already be initialized and all filters must have
+// the same width and depth. The filters do not need to contain the same number of items.
 // Returns OK on success or an error if the filters could not be merged.
 // For more information - https://redis.io/commands/cms.merge/
 func (c cmdable) CMSMergeWithWeight(ctx context.Context, destKey string, sourceKeys map[string]int64) *StatusCmd {