Drop safe level support in more recent Rubies.
The rb_set_safe_level
is available approximately since Ruby 1.8.0, but the
RUBY_SAFE_LEVEL_MAX was available since Ruby 2.1, until it was dropped
in Ruby 3.0 altogether with Ruby safe levels [1].
The rb_set_safe_level
is available approximately since Ruby 1.8.0, but the
RUBY_SAFE_LEVEL_MAX was available since Ruby 2.1, until it was dropped
in Ruby 3.0 altogether with Ruby safe levels [1].