Odd test output in bad_import.carbon after LLVM upgrade in #7413

As noted in https://github.com/carbon-language/carbon-lang/pull/7413#discussion_r3468517496, there's some new output that looks odd:

// CHECK:STDERR: fail_import_cpp_library_file_with_quotes.carbon:[[@LINE+10]]:13: error: invalid suffix on literal; C++11 requires a space between literal and identifier [CppInteropParseError]
// CHECK:STDERR:    18 | #include "\"foo.h\""
// CHECK:STDERR:       |             ^
// CHECK:STDERR:       |              {{}}

// CHECK:STDERR: fail_import_cpp_library_file_with_quotes.carbon:[[@LINE+5]]:13: warning: extra tokens at end of #include directive [CppInteropParseWarning]
// CHECK:STDERR:    18 | #include "\"foo.h\""
// CHECK:STDERR:       |             ^
// CHECK:STDERR:       |             //