WarpXInitEB: fix " int eb_update" shadowing "std::array< std::unique_ptr<amrex::iMultiFab>,3> & eb_update"

[lucafedeli88]

This PR fixes the following issue:

/home/vsts/work/1/s/Source/EmbeddedBoundary/WarpXInitEB.cpp:366:25: warning: declaration of ‘int eb_update’ shadows a parameter [-Wshadow]
  366 |                     int eb_update = 1;
      |                         ^~~~~~~~~
/home/vsts/work/1/s/Source/EmbeddedBoundary/WarpXInitEB.cpp:296:56: note: shadowed declaration is here
  296 |     std::array< std::unique_ptr<amrex::iMultiFab>,3> & eb_update,
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~

Found in https://dev.azure.com/ECP-WarpX/WarpX/_build/results?buildId=20383&view=logs&j=8aa019fd-d859-51bf-081f-826e7fa9e37a