Fix hmdb51 and ucf101 typo (#1420)

* Fix hmdb51.py typo

* Fix ucf101.py typo

Author: jaesuny

torchvision/datasets/hmdb51.py

@@ -9,7 +9,7 @@
 
 class HMDB51(VisionDataset):
     """
-    HMDB51 <http://serre-lab.clps.brown.edu/resource/hmdb-a-large-human-motion-database/>`_
+    `HMDB51 <http://serre-lab.clps.brown.edu/resource/hmdb-a-large-human-motion-database/>`_
     dataset.
 
     HMDB51 is an action recognition video dataset.

torchvision/datasets/ucf101.py

@@ -9,7 +9,7 @@
 
 class UCF101(VisionDataset):
     """
-    UCF101 <https://www.crcv.ucf.edu/data/UCF101.php>`_ dataset.
+    `UCF101 <https://www.crcv.ucf.edu/data/UCF101.php>`_ dataset.
 
     UCF101 is an action recognition video dataset.
     This dataset consider every video as a collection of video clips of fixed size, specified