* server : use common_token_to_piece instead of common_detokenize
This commit replaces the call to common_detokenize with
common_token_to_piece in the populate_token_probs.
The motivation for this change is to avoid an issue where
common_detokenize would remove the word boundary character for tokens,
which caused a regression in the server generated token probabilities.
Resolves: https://github.com/ggerganov/llama.cpp/issues/11728
* squash! server : use common_token_to_piece instead of common_detokenize
Use common_token_to_piece for post_sampling_probs as well.