DOC: Update MC Stan links in Examples (#2084)

* DOC: Update the MC Stan link to Baseball example

* DOC: Update the MC Stan link to Predator-Prey Model

Author: star1327p

examples/baseball.py

@@ -40,7 +40,7 @@
 **References:**
 
     1. Carpenter B. (2016), `"Hierarchical Partial Pooling for Repeated Binary Trials"
-       <http://mc-stan.org/users/documentation/case-studies/pool-binary-trials.html/>`_.
+       <https://mc-stan.org/learn-stan/case-studies/pool-binary-trials.html>`_.
     2. Efron B., Morris C. (1975), "Data analysis using Stein's estimator and its
        generalizations", J. Amer. Statist. Assoc., 70, 311-319.
     3. Neal, R. (2012), "MCMC using Hamiltonian Dynamics",

examples/ode.py

@@ -13,7 +13,7 @@
 **References:**
 
     1. Bob Carpenter (2018), `"Predator-Prey Population Dynamics: the Lotka-Volterra model in Stan"
-       <https://mc-stan.org/users/documentation/case-studies/lotka-volterra-predator-prey.html/>`_.
+       <https://mc-stan.org/learn-stan/case-studies/lotka-volterra-predator-prey.html>`_.
     2. https://en.wikipedia.org/wiki/Lotka-Volterra_equations
     3. http://people.whitman.edu/~hundledr/courses/M250F03/M250.html