Remove the CMake machinery for the Metis/Parmetis compatibility layer:
it has zero users and complicates things due to the separate "metis"
output.

Notably, the assumption in 'SCOTCHConfig.cmake' is that *metisTargets.cmake
are in the same directory, which is not the case here.  Furthermore,
'*metisTargets-relwithdebuginfo.cmake' assumes 'libscotchmetis*.so*' is
available under '_IMPORT_PREFIX', which is only the case when
'libscotchmetis*.so' is installed in the same directory as 'libscotch.so'.

diff --git a/cmake/SCOTCHConfig.cmake.in b/cmake/SCOTCHConfig.cmake.in
index ec52ac5..4ce5c30 100644
--- a/cmake/SCOTCHConfig.cmake.in
+++ b/cmake/SCOTCHConfig.cmake.in
@@ -77,9 +77,3 @@ if(@BUILD_LIBESMUMPS@)
     include("${CMAKE_CURRENT_LIST_DIR}/ptesmumpsTargets.cmake")
   endif()
 endif()
-if(@BUILD_LIBSCOTCHMETIS@)
-  include("${CMAKE_CURRENT_LIST_DIR}/scotchmetisTargets.cmake")
-  if(@BUILD_PTSCOTCH@)
-    include("${CMAKE_CURRENT_LIST_DIR}/ptscotchparmetisTargets.cmake")
-  endif()
-endif()