C++20 concepts require a semicolon after the braces

I have a code part like:
```C++
template <typename T>
concept IndexableToChar = requires(T t) {
  { t[0] } -> std::convertible_to<char>;
};
```

And cpplint says `You don't need a ; after a }  [readability/braces] [4]`. But here this `;` is needed, otherwise there will be compiling error.