Fix compiler warnings in objspace_dump.c when assertions are turned on

Example:

```
In file included from ../../../include/ruby/defines.h:72,
                 from ../../../include/ruby/ruby.h:23,
                 from ../../../gc.h:3,
                 from ../../../ext/objspace/objspace_dump.c:15:
../../../ext/objspace/objspace_dump.c: In function ‘dump_append_ld’:
../../../ext/objspace/objspace_dump.c:95:26: warning: comparison of integer expressions of different signedness: ‘long unsigned int’ and ‘int’ [-Wsign-compare]
   95 |     RUBY_ASSERT(required <= width);
      |                          ^~
```

0 files changed, 0 insertions, 0 deletions