Fix an incorrect autocorrect for Lint/OrAssignmentToConstant

[koic]

This PR fixes the following incorrect autocorrect for Lint/OrAssignmentToConstant when using or-assignment to a constant in method definition.

def foo
  M::N ||= 42
end

$ ruby -v
ruby 3.2.1 (2023-02-08 revision 31819e82c8) [x86_64-darwin19]
$ ruby -c example.rb
Syntax OK
$ bundle exec rubocop --only Lint/OrAssignmentToConstant -a
(snip)

Offenses:

example.rb:2:8: W: Lint/OrAssignmentToConstant: Avoid using or-assignment with constants.
  M::N ||= 42
       ^^^

1 file inspected, 1 offense detected

def foo
  M::N = 42
end

$ ruby -c example.rb
example.rb: example.rb:2: dynamic constant assignment (SyntaxError)
  M::N = 42
  ^~~~

It's reasonable to display the offense, but it wouldn't be reasonable to have this syntax error caused by autocorrection.

---

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• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.