At the end of a cycle, the non-generational mode usage report has an errant reference to 'generation':
```
GC(1) At end of GC: generation used: 835M ...
```
After this change, the message is:
```
GC(0) At end of GC: used: 1793K ...
```

The message is unchanged for the generational mode:
```
GC(0) At end of Concurrent Global GC: Young generation used: 1544K ...
GC(0) At end of Concurrent Global GC: Old generation used: 0B ...

```