llama.cpp: fix warning message (#11839)

llama.cpp: fix warning message (#11839)

There was a typo-like error, which would print the same number twice if
request is received with n_predict > server-side config.

Before the fix:
```
slot launch_slot_: id  0 | task 0 | n_predict = 4096 exceeds server configuration, setting to 4096
```

After the fix:
```
slot launch_slot_: id  0 | task 0 | n_predict = 8192 exceeds server configuration, setting to 4096
```