llama: fix deprecation message: vocabable -> vocab

[dwrensha]

Fixes a mispelled deprecation message that was added in afa8a9e.

The message is supposed to refer to

llama.cpp/include/llama.h

Line 934 in 7a689c4

LLAMA_API const char * llama_vocab_get_text(const struct llama_vocab * vocab, llama_token token);