ci : use Pythia models instead of OpenLlama (#7470)
* ci : start using Pythia models over OpenLlama
ggml-ci
* ci : disable q2_k ppl tests
* ci : use convert-hf-to-gguf.py
* ci : update gg_get_model
* ci : fix convert outfile name
ggml-ci
* llama : gptneox arch use F32 attn prec
ggml-ci
