Suppress unused-result warnings
Suppress unused-result warnings

* Hide read function warning in string_spec_RSTRING_PTR_read function

* The type of `read` may be `ssize_t`

Co-authored-by: Nobuyoshi Nakada <7ff6b48c65ca5c8d3a6019be17b241e7b4763d9e@ruby-lang.org>
ruby/spec,nobu/rubyspec,nobu/rubyspec,ruby/spec,nobu/rubyspec,ruby/spec