Upgrade nlohmann

Current version of nlohmann has some issues with c++20.  Upgrade it.

Tested:
Built bmcweb with
https://gerrit.openbmc-project.xyz/c/openbmc/entity-manager/+/47575 and
build succeeded.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ia8c42f8901b0e3ef613a0fe66ee92742d1680b6c
1 file changed