Fix typo in the docstring of the Beta distribution (#7469)

* Fix typo in the docstring of the Beta distribution

* Update edit to Beta docstring

Author: erik-werner

pymc/distributions/continuous.py

@@ -1118,8 +1118,8 @@ class Beta(UnitContinuous):
 
        \text{where } \kappa = \frac{\mu(1-\mu)}{\sigma^2} - 1
 
-       \alpha = \mu * \nu
-       \beta = (1 - \mu) * \nu
+       \alpha &= \mu * \nu \\
+       \beta &= (1 - \mu) * \nu
 
     Parameters
     ----------