Make pbr bloom example compile

src/8.guest/2022/6.physically_based_bloom/6.bloom_final.fs

@@ -42,7 +42,7 @@ void main()
         result = bloom_none(); break;
     }
     // tone mapping
-    vec3 result = vec3(1.0) - exp(-hdrColor * exposure);
+    result = vec3(1.0) - exp(-result * exposure);
     // also gamma correct while we're at it
     const float gamma = 2.2;
     result = pow(result, vec3(1.0 / gamma));