fix comment (#1798)

diff --git a/Lib/random.py b/Lib/random.py
index b54d524..e1c2c2b 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -540,7 +540,7 @@
                     return x * beta
 
         elif alpha == 1.0:
-            # expovariate(1)
+            # expovariate(1/beta)
             u = random()
             while u <= 1e-7:
                 u = random()