Update fmt to version 6.1.2

Author: scamille

engine/util/fmt/README.md

@@ -14,6 +14,5 @@ std::string s = fmt::format("{0}{1}{0}", "abra", "cad");
 
 SimC Integration:
 -----------------
-* Release 6.0.0 from https://github.com/fmtlib/fmt/releases/tag/6.0.0
-* rename .cc files to .cpp for simpler integration into our build systems.
-* applied workaround for VS2019 bug: https://github.com/fmtlib/fmt/pull/1328/commits/35658bf42d6fc3eb2b3b5f78f85a0abd8f9b6817
+* Release 6.1.2 from https://github.com/fmtlib/fmt/releases/tag/6.1.2
+* rename .cc files to .cpp for simpler integration into our build systems.