Make binding.eval Ruby 3.0 compatible.
Make binding.eval Ruby 3.0 compatible.

Ruby 3.0 changes behavior of `binding.eval` [[1]] resulting in test
failure:

~~~
WebConsole::EvaluatorTest#test_Evaluator_callers_are_cleaned_up_of_unneeded_backtraces [/home/travis/build/rails/web-console/test/web_console/evaluator_test.rb:63]:
--- expected
+++ actual
@@ -1,3 +1,3 @@
 "RuntimeError: oops
-\tfrom /home/travis/build/rails/web-console/test/web_console/evaluator_test.rb:61:in `block in <class:EvaluatorTest>'
+\tfrom (eval):1:in `block in <class:EvaluatorTest>'
~~~

Fixes #301

[1]: https://bugs.ruby-lang.org/issues/17419

rails/web-console,rails/web-console,rails/web-console,rails/web-console