Minor doc string fixes (#3528)

(Definitional) Change "K dimensional simplex space" to "K - 1 dimensional simplex space"
Update doc strings of sumto1 and stick_breaking transforms in transforms.py

pymc3/distributions/transforms.py

@@ -400,7 +400,7 @@ def jacobian_det(self, y):
 
 class SumTo1(Transform):
     """
-    Transforms K dimensional simplex space (values in [0,1] and sum to 1) to K - 1 vector of values in [0,1]
+    Transforms K - 1 dimensional simplex space (k values in [0,1] and that sum to 1) to a K - 1 vector of values in [0,1]
     This Transformation operates on the last dimension of the input tensor.
     """
 
@@ -430,7 +430,7 @@ def jacobian_det(self, x):
 
 class StickBreaking(Transform):
     """
-    Transforms K dimensional simplex space (values in [0,1] and sum to 1) to K - 1 vector of real values.
+    Transforms K - 1 dimensional simplex space (k values in [0,1] and that sum to 1) to a K - 1 vector of real values.
     Primarily borrowed from the STAN implementation.
 
     Parameters