Bump transformers from 4.38.0 to 4.50.0 in /lessons/5-NLP

Bumps [transformers](https://github.com/huggingface/transformers) from 4.38.0 to 4.50.0.
- [Release notes](https://github.com/huggingface/transformers/releases)
- [Commits](https://github.com/huggingface/transformers/compare/v4.38.0...v4.50.0)

---
updated-dependencies:
- dependency-name: transformers
  dependency-version: 4.50.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

lessons/5-NLP/requirements-pytorch.txt

@@ -12,4 +12,4 @@ torchaudio==0.8.1
 torchinfo==0.0.8
 torchtext==0.9.1
 torchvision==0.9.1
-transformers==4.38.0
+transformers==4.50.0

lessons/5-NLP/requirements-tf.txt

@@ -10,4 +10,4 @@ scipy
 TensorFlow
 TensorFlow_datasets
 TensorFlow_text
-transformers==4.38.0
+transformers==4.50.0