Synchronized the text in book and src with fmin in refract

Author: trevordblack

CHANGELOG.md

@@ -4,6 +4,7 @@ Change Log -- Ray Tracing in One Weekend
 # v3.2.2 (in progress)
 
 ### Common
+  - Fix: Addded `fmin` to book text for `cos_theta` of `refract`
 
 ### In One Weekend
 

books/RayTracingInOneWeekend.html

@@ -2380,7 +2380,7 @@
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
     vec3 refract(const vec3& uv, const vec3& n, double etai_over_etat) {
-        auto cos_theta = dot(-uv, n);
+        auto cos_theta = fmin(dot(-uv, n), 1.0);
         vec3 r_out_perp =  etai_over_etat * (uv + cos_theta*n);
         vec3 r_out_parallel = -sqrt(fabs(1.0 - r_out_perp.length_squared())) * n;
         return r_out_perp + r_out_parallel;