docs: fix description

Signed-off-by: Athan <kgryte@gmail.com>

Author: kgryte

lib/node_modules/@stdlib/stats/strided/dztest2/docs/types/index.d.ts

@@ -87,7 +87,7 @@ interface BaseResults {
 	ci: Float64Array;
 
 	/**
-	* Value of the mean under the null hypothesis
+	* Difference in means under the null hypothesis.
 	*/
 	nullValue: number;