Revert "examples/hello-world: make it fail"

This reverts commit 3d2d242d2cdf0e94839529da61f9ea54b507b3f9.

examples/hello-world/main.c

@@ -23,7 +23,7 @@
 
 int main(void)
 {
-    puts("Hello World!")
+    puts("Hello World!");
 
     printf("You are running RIOT on a(n) %s board.\n", RIOT_BOARD);
     printf("This board features a(n) %s MCU.\n", RIOT_MCU);