fix(peft): correct typo in flattening operation error messages
Author: leaderofARS
Pull request: yes

# What does this PR do?                                                                                                                                  
                                                                                                                                                             
This PR corrects a minor spelling typo in the PEFT integration error messages. Specifically, it corrects the misspelling of "flattening operation" (previously written as "flatteing operatio") in two `NotImplementedError` messages within `src/transformers/integrations/peft.py` to improve clarity.      
                                                                                                                                                             
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- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).                                                   
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- [ ] Did you write any new necessary tests?                                                                                                             
                                                                                                                                                             
                                                                                                                                                             
## Who can review?                                                                                                                                       
                                                                                                                                                             
@BenjaminBossan 
@githubnemo 

Comments:
View the CircleCI Test Summary for this PR:

https://huggingface.co/spaces/transformers-community/circle-ci-viz?pr=46538&sha=43379b

The tests failed due to a transient network error (httpx.RemoteProtocolError). Could someone re-run the CI jobs?

Sorry, we're trying to avoid these small typo PRs right now! We'll do an agent pass at some point to just fix all of them, and in the meantime we want to keep PRs for significant stuff because our maintainers are struggling with the flood of agent submissions