Fix to broken build in clang

[daavid00]

This is the error (macOS, clang):

/Users/dmar/Github/opm/opm-simulators/opm/simulators/wells/ParallelWellInfo.cpp:642:13: error: call to member function 'broadcast' is ambiguous
  642 |         ser.broadcast(rankWithFirstPerf_, res);
/Users/dmar/Github/opm/opm-simulators/opm/simulators/utils/MPISerializer.hpp:46:10: note: candidate function [with T = const int]
   46 |     void broadcast(T& data, int root = 0)
      |          ^
/Users/dmar/Github/opm/opm-simulators/opm/simulators/utils/MPISerializer.hpp:73:10: note: candidate function [with Args = <int &>]
   73 |     void broadcast(int root, Args&&... args)

This 'hack 'fixes the building (for sure there is a more elegant (proper) fix, if someone has one, please do a PR and I will close this one.

[daavid00]

jenkins build this please

[atgeirr]

I see this error as well. I will try to make a more fundamental fix, but if I fail I will merge this workaround.

[atgeirr]

Made a different fix in #6180.