fix typo and missing semicolon

Author: yixuan

src/stan-users-guide/reparameterization.qmd

@@ -102,13 +102,13 @@ model {
 The new parameters, `phi` and `lambda`, are declared in the
 parameters block and the parameters for the Beta distribution,
 `alpha` and `beta`, are declared and defined in the
-transformed parameters block.  And If their values are not of interest,
+transformed parameters block.  And if their values are not of interest,
 they could instead be defined as local variables in the model as
 follows.
 
 ```stan
 model {
-  real alpha = lambda * phi
+  real alpha = lambda * phi;
   real beta = lambda * (1 - phi);
   // ...
   for (n in 1:N) {