is_flash_attn_available has been renamed in transformers.utils

[simrathanspal]

Updated is_flash_attn_available to is_flash_attn_2_available

transformer.utils - https://github.com/huggingface/transformers/blob/main/src/transformers/utils/init.py

PR - https://github.com/huggingface/transformers/pull/26785