Fix date math zone test to use negative minutes

Joda classes for timezones accepted positive minutes when a negative
hours was used, but Java time expects negative minutes when negative
hours are used. This commit fixes tests to ensure negative minutes are
used with negative hours.

closes elastic#78783

server/src/test/java/org/elasticsearch/cluster/metadata/DateMathExpressionResolverTests.java

@@ -126,8 +126,7 @@ public void testExpression_MixedArray() throws Exception {
         assertThat(result.get(3), equalTo(".logstash-" +
             formatDate("uuuu.MM", dateFromMillis(context.getStartTime()).withDayOfMonth(1))));
     }
-
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/78783")
+
     public void testExpression_CustomTimeZoneInIndexName() throws Exception {
         ZoneId timeZone;
         int hoursOffset;
@@ -138,6 +137,9 @@ public void testExpression_CustomTimeZoneInIndexName() throws Exception {
         } else {
             hoursOffset = randomIntBetween(-11, 13);
             minutesOffset = randomIntBetween(0, 59);
+            if (hoursOffset < 0) {
+                minutesOffset = -minutesOffset;
+            }
             timeZone = ZoneOffset.ofHoursMinutes(hoursOffset, minutesOffset);
         }
         ZonedDateTime now;