Remove redundant requirements with transformers.

examples/distillation/requirements.txt

@@ -1,6 +1,7 @@
+transformers
+
 gitpython==3.0.2
 tensorboard>=1.14.0
 tensorboardX==1.8
 psutil==5.6.3
 scipy==1.3.1
-transformers

examples/summarization/requirements.txt

@@ -1,9 +1,5 @@
-# progress bars in model download and training scripts
+transformers
-tqdm
+
-# Accessing files from S3 directly.
-boto3
-# Used for downloading models over HTTP
-requests
 # For ROUGE
 nltk
 py-rouge