Cleaned some redundant lines

```while not args.unconditional:
   if not args.unconditional:
```
These lines have been updated

examples/run_gpt2.py

@@ -83,8 +83,8 @@ def run_model():
     elif args.length > model.config.n_ctx:
         raise ValueError("Can't get samples longer than window size: %s" % model.config.n_ctx)
 
-    while not args.unconditional:
     if not args.unconditional:
+        while True:
             raw_text = input("Model prompt >>> ")
             while not raw_text:
                 print('Prompt should not be empty!')
@@ -94,8 +94,8 @@ def run_model():
             for _ in range(args.nsamples // args.batch_size):
                 out = sample_sequence(
                     model=model, length=args.length,
-                context=context_tokens if not args.unconditional else None,
-                start_token=enc.encoder['<|endoftext|>'] if args.unconditional else None,
+                    context=context_tokens,
+                    start_token=None,
                     batch_size=args.batch_size,
                     temperature=args.temperature, top_k=args.top_k, device=device
                 )