pl version: examples/requirements.txt is single source of truth (#6309)

examples/text-classification/run_pl.sh

-# Install newest ptl.
-pip install -U git+http://github.com/PyTorchLightning/pytorch-lightning/
 # Install example requirements
 pip install -r ../requirements.txt
 

examples/token-classification/run_pl.sh

 #!/usr/bin/env bash
 
-# Install newest ptl.
-pip install -U git+http://github.com/PyTorchLightning/pytorch-lightning/
 # for seqeval metrics import
 pip install -r ../requirements.txt
 
@@ -40,4 +38,4 @@ python3 run_pl_ner.py --data_dir ./ \
 --train_batch_size $BATCH_SIZE \
 --seed $SEED \
 --do_train \
---do_predict
\ No newline at end of file
+--do_predict