Update DIModule test after LLVM change (#3473)

Update a test for llvm-project commit `5bc7b9d462f0 ("[llvm][dwarfdump]
Print the name (if available) of entities referenced by DW_AT_import
(#171859)", 2025-12-12)`.

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@fedea4be9304a

Author: svenvh

llvm-spirv/test/DebugInfo/X86/dimodule-external-fortran.ll

@@ -40,7 +40,7 @@
 ; CHECK:      DW_TAG_imported_module
 ; CHECK-NEXT:   DW_AT_decl_file
 ; CHECK-NEXT:   DW_AT_decl_line
-; CHECK-NEXT:   DW_AT_import  ([[DIE_ID]])
+; CHECK-NEXT:   DW_AT_import  ([[DIE_ID]] "external_module")
 
 ; When the debugger sees the module being imported is a declaration,
 ; it should go to the global scope to find the module's definition.