[TEST] increase minimum length of randomly generated fields in RandomObjects

We had a couple of unfortunate field name collisions in our CI, where the json duplicate check tripped. Increasing the minimum length of randomly generated field names should decrease the chance of this issue happening again.

test/framework/src/main/java/org/elasticsearch/test/RandomObjects.java

@@ -190,11 +190,11 @@ public final class RandomObjects {
         for (int i = 0; i < numFields; i++) {
             if (currentDepth < 5 && random.nextBoolean()) {
                 if (random.nextBoolean()) {
-                    builder.startObject(RandomStrings.randomAsciiOfLengthBetween(random, 4, 10));
+                    builder.startObject(RandomStrings.randomAsciiOfLengthBetween(random, 6, 10));
                     addFields(random, builder, minNumFields, currentDepth + 1);
                     builder.endObject();
                 } else {
-                    builder.startArray(RandomStrings.randomAsciiOfLengthBetween(random, 4, 10));
+                    builder.startArray(RandomStrings.randomAsciiOfLengthBetween(random, 6, 10));
                     int numElements = randomIntBetween(random, 1, 5);
                     boolean object = random.nextBoolean();
                     int dataType = -1;
@@ -213,7 +213,7 @@ public final class RandomObjects {
                     builder.endArray();
                 }
             } else {
-                builder.field(RandomStrings.randomAsciiOfLengthBetween(random, 4, 10),
+                builder.field(RandomStrings.randomAsciiOfLengthBetween(random, 6, 10),
                         randomFieldValue(random, randomDataType(random)));
             }
         }