[ox/std] Fix unnecessary implicit sign conversion

(synced from 22a7ff74ce)

src/ox/std/fmt.hpp

@@ -153,9 +153,9 @@ template<std::size_t segementCnt>
 [[nodiscard]]
 constexpr Fmt<segementCnt> fmtSegments(StringView fmt) noexcept {
 	Fmt<segementCnt> out;
-	const auto prev = [fmt](int i) -> char {
+	const auto prev = [fmt](std::size_t i) -> char {
 		if (i > 0) {
-			return fmt[static_cast<std::size_t>(i) - 1];
+			return fmt[i - 1];
 		} else {
 			return '\0';
 		}