Fix an incorrect autocorrect for Style/OperatorMethodCall

[koic]

This PR fixes an incorrect autocorrect for Style/OperatorMethodCall when using foo./bar:

% echo 'arg./100.0' | bundle exec rubocop --stdin example.rb -a -d
(snip)

F

Offenses:

example.rb:1:4: C: [Corrected] Style/OperatorMethodCall: Redundant dot detected.
arg./100.0
   ^
example.rb:1:5: F: Lint/Syntax: ambiguous first argument; put parentheses or a space even after the operator
(Using Ruby 2.7 parser; configure using TargetRubyVersion parameter, under AllCops)
arg /100.0
    ^

1 file inspected, 2 offenses detected, 1 offense corrected
====================
arg /100.0

It solves the above Lint/Syntax.

---

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• 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.