[Fix #8081] Fix a false positive for Lint/SuppressedException

[koic]

Fixes #8081.

This PR fixes a false positive for Lint/SuppressedException when empty rescue block in do block.

% cat example.rb
foo do
rescue Foo
  # ok
end

% bundle exec rubocop --only Lint/SuppressedException
(snip)

Inspecting 1 file
W

Offenses:

example.rb:2:1: W: Lint/SuppressedException: Do not suppress exceptions.
rescue Foo
^^^^^^^^^^

1 file inspected, 1 offense detected

do block rescue is a syntax introduced in Ruby 2.5.

---

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• Wrote good commit messages.
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• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
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