[flang] Disable three error tests (#122)

Some interoperability checks are being relaxed in an upcoming
change to the compiler, and an error has been downgraded to a
portability warning.  This will cause these three tests to
"fail" due to lack of a fatal error, so I'm disabling them
now to prevent build bot failures.

If I knew how to run these tests with "-pedantic -Werror",
I would do that instead.

Author: klausler

Fortran/gfortran/regression/DisabledFiles.cmake

@@ -1430,6 +1430,9 @@ file(GLOB FAILING_FILES CONFIGURE_DEPENDS
   # Tests that used to be hard errors, are now warnings, need -pedantic to
   # observe them
   interface_6.f90
+  interop_params.f03
+  iso_c_binding_class.f03
+  pr85877.f90
 
   # Tests that would be errors if we supported options to enable checks
   dec_structure_24.f90