Updated pymc.Gamma docstring (#5496)

* Updated pymc.Gamma docstring

* address review comments

pymc/distributions/continuous.py

@@ -2244,6 +2244,7 @@ class Gamma(PositiveContinuous):
            \frac{\beta^{\alpha}x^{\alpha-1}e^{-\beta x}}{\Gamma(\alpha)}
 
     .. plot::
+        :context: close-figs
 
         import matplotlib.pyplot as plt
         import numpy as np
@@ -2278,13 +2279,13 @@ class Gamma(PositiveContinuous):
 
     Parameters
     ----------
-    alpha: float
+    alpha : tensor_like or float, optional
         Shape parameter (alpha > 0).
-    beta: float
+    beta : tensor_like or float, optional
         Rate parameter (beta > 0).
-    mu: float
+    mu : tensor_like or float, optional
         Alternative shape parameter (mu > 0).
-    sigma: float
+    sigma : tensor_like or float, optional
         Alternative scale parameter (sigma > 0).
     """
     rv_op = gamma
@@ -2339,7 +2340,7 @@ def logcdf(value, alpha, inv_beta):
 
         Parameters
         ----------
-        value: numeric or np.ndarray or `TensorVariable`
+        value : tensor_like
             Value(s) for which log CDF is calculated. If the log CDF for
             multiple values are desired the values must be provided in a numpy
             array or `TensorVariable`.