Restore a pending test for processing a regex with regopt

This PR reverts a pending test of rubocop#10432 because jruby/jruby#7113
has been resolved in JRuby 9.3.9.0.

## JRuby 9.3.3.0

`RegexpError` error will occur:

```console
% rbenv local jruby-9.3.3.0
% ruby -e "Regexp.new('\x82', Regexp::NOENCODING)"
RegexpError: invalid multibyte escape: /\x82/
  initialize at org/jruby/RubyRegexp.java:956
         new at org/jruby/RubyClass.java:893
      <main> at -e:1
```

## JRuby 9.3.9.0 and JRuby 9.4.1.0

No errors:

```console
% rbenv local jruby-9.3.9.0
% ruby -e "Regexp.new('\x82', Regexp::NOENCODING)"

% rbenv local jruby-9.4.1.0
% ruby -e "Regexp.new('\x82', Regexp::NOENCODING)"
```

spec/rubocop/cop/variable_force_spec.rb

@@ -28,9 +28,7 @@
       end
     end
 
-    # FIXME: Remove `broken_on: jruby` when JRuby incompatible is resolved:
-    # https://github.com/jruby/jruby/issues/7113
-    context 'when processing a regex with regopt', broken_on: :jruby do
+    context 'when processing a regex with regopt' do
       let(:node) { parse_source('/\x82/n =~ "a"').ast }
 
       it 'does not raise an error' do