[Java] Array of Varchar example is missleading

```java
import org.apache.arrow.memory.BufferAllocator;
import org.apache.arrow.memory.RootAllocator;
import org.apache.arrow.vector.VarCharVector;

try(
BufferAllocator allocator = new RootAllocator();
VarCharVector varCharVector = new VarCharVector("varCharVector", allocator);
) {
varCharVector.allocateNew(3);
varCharVector.set(0, "one".getBytes());
varCharVector.set(1, "two".getBytes());
varCharVector.set(2, "three".getBytes());
varCharVector.setValueCount(3);

System.out.print(varCharVector);
}
```

This snippet only works because few short strings are written. allocateNew does not grow the data buffer depending on the size of n (3 in this case). The example should either call the allocateNew method variant that specifies the byte count, use setSafe, or have a comment about this.

Find the Java VarCharVector example shown in the issue and read its surrounding cookbook page. Confirm the allocation behavior, then update the example to use an allocation method that specifies the byte count or setSafe, or add a warning comment; done when the example no longer implies that allocateNew(3) safely handles strings of arbitrary length.

Written by the indexing model from the issue text.