ci: simplify diffusers install — force-reinstall from PyPI, drop redundant deps

The Docker image already has transformers/accelerate/peft. Only diffusers
needs overriding (image has dev version > latest PyPI release).
--force-reinstall --no-deps does this in one line.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Titus-von-Koeller

.github/workflows/tests-integration-nightly.yml

@@ -169,8 +169,7 @@ jobs:
       - name: Install bnb + diffusers from PyPI (overriding image versions)
         run: |
           pip install "bitsandbytes[test] @ ${BNB_WHEEL_URL}"
-          pip uninstall -y diffusers
-          pip install diffusers transformers accelerate peft
+          pip install --force-reinstall --no-deps diffusers
 
       - name: Clone diffusers matching installed version
         run: |