fix Zero or negative time interval not supported

Author: Hendrik Muhs

client/rest-high-level/src/test/java/org/elasticsearch/client/transform/transforms/pivot/hlrc/DateHistogramGroupSourceTests.java

@@ -74,7 +74,7 @@ public static DateHistogramGroupSource randomDateHistogramGroupSource() {
             dateHistogramGroupSource = new DateHistogramGroupSource(
                 field,
                 scriptConfig,
-                new DateHistogramGroupSource.FixedInterval(new DateHistogramInterval(randomPositiveTimeValue())),
+                new DateHistogramGroupSource.FixedInterval(new DateHistogramInterval(randomTimeValue(1, 100, "d", "h", "ms", "s", "m"))),
                 randomBoolean() ? randomZone() : null
             );
         } else {