[flang] fix skip-external-rtti-definition for ppc (#146826)

PPC does not use comdat. There is no need to check for that in the test,
just remove it.

Fix for https://lab.llvm.org/buildbot/#/builders/201/builds/5278

Author: jeanPerier

flang/test/Integration/skip-external-rtti-definition.F90

@@ -33,9 +33,9 @@ subroutine needs_descriptor(x)
 
 #endif
 
-! LINKONCE-DAG: @_QMmodule_external_type_definitionEXnXt1 = linkonce_odr constant [2 x i8] c"t1", comdat
+! LINKONCE-DAG: @_QMmodule_external_type_definitionEXnXt1 = linkonce_odr constant [2 x i8] c"t1"
 ! LINKONCE-DAG: @_QMmodule_external_type_definitionEXdtXt1 = linkonce_odr constant {{.*}} {
-! LINKONCE-DAG: @_QMmodule_same_unit_type_definitionEXnXt2 = linkonce_odr constant [2 x i8] c"t2", comdat
+! LINKONCE-DAG: @_QMmodule_same_unit_type_definitionEXnXt2 = linkonce_odr constant [2 x i8] c"t2"
 ! LINKONCE-DAG: @_QMmodule_same_unit_type_definitionEXdtXt2 = linkonce_odr constant {{.*}} {
 
 ! EXTERNAL-NOT: @_QMmodule_external_type_definitionEXnXt1