code optimization

```
// org.apache.dubbo.common.utils.CollectionUtils#269
public static Set ofSet(T... values) {
int size = values == null ? 0 : values.length;
if (size < 1) {
return emptySet();
}

float loadFactor = 1f / ((size + 1) * 1.0f);

if (loadFactor > 0.75f) {
loadFactor = 0.75f;
}

Set elements = new LinkedHashSet<>(size, loadFactor);
for (int i = 0; i < size; i++) {
elements.add(values[i]);
}
return unmodifiableSet(elements);
}
```
in this code, loadFactor is never large than o.75f and too small can lead to frequent rehash, so set loadFactor o.75f is ok?