Fix false positive for Metrics/MethodLength and Metrics/BlockLength

[meganemura]

Metrics/MethodLength and Metrics/BlockLength cops count lines of code incorrectly.
These cops count not only inside body but also definition/receiver.

Example for Metrics/BlockLength:

# frozen_string_literal: true
[    # This line is treated as beginning of the block in counting logic
  1,
  2,
  3,
  4,
  5,
  6,
  7,
  8,
  9,
  10,
  11,
  12,
  13,
  14,
  15,
  16,
  17,
  18,
  19,
  20,
  21,
  22,
  23,
  24
].each do |x|  # 25
  puts x       # 26
end

RuboCop says

test.rb:2:1: C: Metrics/BlockLength: Block has too many lines. [26/25]
[ ...
^

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Used the same coding conventions as the rest of the project.
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• All tests are passing.
• The new code doesn't generate RuboCop offenses.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.

[savef]

Good find. 👍