[examples] update transfomers version (#665)

update transfomrers version in example

examples/dreambooth/README.md

@@ -11,7 +11,7 @@ Before running the scripts, make sure to install the library's training dependen
 
 ```bash
 pip install git+https://github.com/huggingface/diffusers.git
-pip install -r requirements.txt
+pip install -U -r requirements.txt
 ```
 
 And initialize an [🤗Accelerate](https://github.com/huggingface/accelerate/) environment with:

examples/dreambooth/requirements.txt

 accelerate
 torchvision
-transformers
+transformers>=4.21.0
 ftfy
 tensorboard
 modelcards
\ No newline at end of file

examples/textual_inversion/README.md

@@ -17,7 +17,7 @@ Colab for inference
 Before running the scripts, make sure to install the library's training dependencies:
 
 ```bash
-pip install diffusers[training] accelerate transformers
+pip install diffusers"[training]" accelerate "transformers>=4.21.0"
 ```
 
 And initialize an [🤗Accelerate](https://github.com/huggingface/accelerate/) environment with:

examples/textual_inversion/requirements.txt

 accelerate
 torchvision
-transformers
+transformers>=4.21.0