Updated metrics/classification/precision_recall.py (PL^5348)

There was a typo in Documentation of Code of the ```compute()``` function of ```Recall``` metric at line 210. It said "Computes accuracy over state." which should have been "Computes recall over state."

(cherry picked from commit d568533b6ba0768ac7a6d028b3a25c5970a65e80)
(cherry picked from commit d2b7faf452890225dd4b7b62634bcbd8d0fdff96)

pytorch_lightning/metrics/classification/precision_recall.py

@@ -207,7 +207,7 @@ class Recall(Metric):
 
     def compute(self):
         """
-        Computes accuracy over state.
+        Computes recall over state.
         """
         if self.average == 'micro':
             return self.true_positives.sum().float() / (self.actual_positives.sum() + METRIC_EPS)