Bump rubocop to 0.49.1 and rubocop-rspec to 1.15.1

What does this MR do?

• Bump rubocop from 0.47.1 to 0.49.1 ~"gem update"
• Bump rubocop-rspec to 1.15.1 ~"gem update"
• Adapt some rubocop rules renamed from Style to Layout ~backstage
• Disable the following Cops newly introduced after 0.47.1 (through 0.49.1) but offended.

   8 Layout/EmptyLineAfterMagicComment
  10 Layout/EmptyLinesAroundExceptionHandlingKeywords
  23 Layout/IndentHeredoc
  79 Style/FormatStringToken
   4 Style/InverseMethods
   5 Style/MultipleComparison
 543 Style/SymbolArray
   3 Style/YodaCondition
 170 Lint/AmbiguousBlockAssociation
   1 Performance/Caller
 101 Rails/ApplicationRecord
  82 Rails/Blank
  18 Rails/Present
   1 Rails/RelativeDateConstant

Are there points in the code the reviewer needs to double check?

No.

Why was this MR needed?

Because rubocop has CVE-2017-8418. To keep gems up to date.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [n/a] Documentation created/updated
• [n/a] API support added
• Tests
  • [n/a] Added for this feature/bug
  • All builds are passing
• [n/a] Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #34869 (closed)