Description: GCC 10.0.1 started to warn on redundant comparisons. Horizon
builds with -Werror, so this warning is turned into an error. Upstream fixed this,
so backport to Horizon.

Based on https://github.com/nlohmann/json/pull/2144/commits/23051df2c71dd3f9698e01de3cbfab0034c6e50e

diff --git a/3rdparty/json.hpp b/3rdparty/json.hpp
index 06da815..58e3f27 100644
--- a/3rdparty/json.hpp
+++ b/3rdparty/json.hpp
@@ -8491,7 +8491,7 @@ scan_number_done:
         std::string result;
         for (const auto c : token_string)
         {
-            if ('\x00' <= c and c <= '\x1F')
+            if (static_cast<unsigned char>(c) <= '\x1F')
             {
                 // escape control characters
                 std::array<char, 9> cs{{}};