[Fortran] Disable reduction test that is incorrectly passing

The tests is not catching the intended semantic errors and will
stop failing when the following patch lands. Disable in advance.
https://github.com/llvm/llvm-project/pull/70822
diff --git a/Fortran/gfortran/regression/gomp/DisabledFiles.cmake b/Fortran/gfortran/regression/gomp/DisabledFiles.cmake
index 5177b85..bfa5379 100644
--- a/Fortran/gfortran/regression/gomp/DisabledFiles.cmake
+++ b/Fortran/gfortran/regression/gomp/DisabledFiles.cmake
@@ -448,5 +448,6 @@
   pr33439.f90
   pr44036-3.f90
   pr78866-2.f90
+  reduction3.f90
   sharing-3.f90
 )