fix: guard BEGIN_OF_TOOL_RESPONSE for Gemma2 and fix f-string in _normalize_token#590

ashiksharonm wants to merge 3 commits intogoogle-deepmind:maingoogle-deepmind/gemma:mainfrom

ashiksharonm:fix/gemma2-sampler-end-tokens-and-normalize-token-fstring-568-579ashiksharonm/gemma:fix/gemma2-sampler-end-tokens-and-normalize-token-fstring-568-579Copy head branch name to clipboard