Tests: Fix failure in InternalGeoBoundsTests (#26112)

This occasionally fails now because if `top` is `-Infinity` (which we sometimes 
test for in randomization), the value might not get changed for the
equals/hashCode tests.

Closes #26107

core/src/test/java/org/elasticsearch/search/aggregations/metrics/geobounds/InternalGeoBoundsTests.java

@@ -121,7 +121,11 @@ public class InternalGeoBoundsTests extends InternalAggregationTestCase<Internal
             name += randomAlphaOfLength(5);
             break;
         case 1:
+            if (Double.isFinite(top)) {
                 top += between(1, 20);
+            } else {
+                top = randomDouble();
+            }
             break;
         case 2:
             bottom += between(1, 20);