Change The printf function of the Hello World code (#30996)

Just changing the printf string of the Hello World code to match the code used later in the article

guide/english/c/index.md

@@ -27,7 +27,7 @@ Now that you have that background, let's start with our 'Hello, World' program.
 
 int main(void)    
 {
-    printf("hello, world\n");  
+    printf("Hello, World!\n");
     return 0;
 }
 ```