Revert "reference/cctype/isspace.md: Created sample implementation"

This reverts commit 3527568.

I've reverted it because it causes confusion.

Author: rotarymars

reference/cctype/isspace.md

@@ -50,12 +50,3 @@ isspace(' ') = 8192
 isspace('\n') = 8192
 isspace('0x0f') = 0
 ```
-
-## 実装例
-```cpp
-int isspace(int ch) {
-  return ch == ' ' || ch == '\t' || ch == '\r' || ch == '\n' || ch == '\v' || ch == '\f';
-}
-```
-
-