Typo: Switch "let" to "int" to make GLSL code valid

Author: BretHudson

src/content/tutorials/en/intro-to-shaders.mdx

@@ -289,7 +289,7 @@ int maxVal = 10;
 if (something) {
   maxVal = 20;
 }
-for (let i = 0; i < 20; i++) {
+for (int i = 0; i < 20; i++) {
   if (i == maxVal) {
     break;
   }