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
```
