Declare hash_frame's constructor noexcept

GCC's -Wnoexcept (an error in CI) flags the emplace_back() into the
hash stack under C++26: the constructor cannot throw, since cbegin() is
noexcept, but it did not say so. dump_frame's constructor is noexcept
for the same reason.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

single_include/nlohmann/json.hpp

@@ -7180,7 +7180,7 @@ std::size_t hash(const BasicJsonType& j, const std::size_t depth = 0)
 template<typename BasicJsonType>
 struct hash_frame
 {
-    hash_frame(const BasicJsonType* value_, std::size_t seed_)
+    hash_frame(const BasicJsonType* value_, std::size_t seed_) noexcept
         : value(value_), position(value_->cbegin()), seed(seed_)
     {}