Update C.c (#1211)

1. `()` function declarations are deprecated in modern C
2. `return 0` at the end of `main` is redundant in modern C

c/C.c

@@ -1,6 +1,5 @@
 #include <stdio.h>
 
-int main() {
+int main(void) {
 	printf("Hello World\n");
-	return 0;
 }