Fix anos::vga_buffer::test_println_many

src/vga_buffer.rs

@@ -163,7 +163,7 @@ fn test_println_simple() {  // 测试单行 println!
 
 #[test_case]
 fn test_println_many() {    // 测试多行 println!
-    for _ in 0..100 {
+    for _ in 0..10 {
         println!("test_println_many output");
     }
 }