C++: do not use fully qualified names in error template parameters

The definition of variables does not use them, so here it is also unnecessary.

For C++11 changes this code:
```
m_one_cat = std::unique_ptr<cat_t>(new cat_t(m__io, this, m__root));
m_one_cat->_read();
{
    // Definition: cat_t* one_cat() { return m_one_cat.get(); }
    std::unique_ptr<cat_t> _ = one_cat();
    if (!(1 == 1)) {
        throw kaitai::validation_expr_error<std::unique_ptr<debug_array_user_t::cat_t>>(one_cat(), _io(), std::string("/seq/0"));
    }
}
```

to this:

```
m_one_cat = std::unique_ptr<cat_t>(new cat_t(m__io, this, m__root));
m_one_cat->_read();
{
    // Definition: cat_t* one_cat() { return m_one_cat.get(); }
    std::unique_ptr<cat_t> _ = one_cat();
    if (!(1 == 1)) {
        throw kaitai::validation_expr_error<std::unique_ptr<cat_t>>(one_cat(), _io(), std::string("/seq/0"));
    }
}
```

shared/src/main/scala/io/kaitai/struct/languages/CppCompiler.scala

@@ -1039,7 +1039,7 @@ class CppCompiler(
     case UndecidedEndiannessError => "kaitai::undecided_endianness_error"
     case ConversionError => "std::invalid_argument"
     case validationErr: ValidationError =>
-      val cppType = kaitaiType2NativeType(validationErr.dt, true)
+      val cppType = kaitaiType2NativeType(validationErr.dt)
       val cppErrName = validationErr match {
         case _: ValidationNotEqualError => "validation_not_equal_error"
         case _: ValidationLessThanError => "validation_less_than_error"