Add block comment example and remove whitespace (#28816)

* Add block comment example and remove whitespace

* fix: capitalized string to match output

* fix: removed >

guide/english/c/hello-world/index.md

@@ -10,13 +10,13 @@ To write on console you can use the function `printf()` contained in the library
  ```C
  #include <stdio.h>
  
+ /* Any text in between these two characters is a block comment.
+    Block comments, unlike inline comments, can span multiple lines.
+    Comments are ignored by the compiler and will not be executed.
+  */
  int main(void)
  {
-     printf("hello, world\n");  // lines starting with this (//) are called comments..
-
-     //this code prints "Hello World!"
-     printf("Hello World!\n"); //<-- the \n character prints a newline after the string  
-
+     printf("Hello, World!\n");  // lines starting with double forward-slash are called inline comments..
      return 0;
  }
  ```
@@ -31,7 +31,7 @@ To write on console you can use the function `printf()` contained in the library
 
  ## Output:
  ```
- >Hello, World!
+ Hello, World!
  ```
  
  #### More Information