fixup! Mute Rubocop

There won't be three levels of nesting in RSpec 4 when we remove the
outer check.

Author: pirj

lib/rspec/core/formatters/exception_presenter.rb

@@ -57,7 +57,7 @@ def formatted_cause(exception)
 
               unless last_cause.backtrace.nil? || last_cause.backtrace.empty?
                 lines = backtrace_formatter.format_backtrace(last_cause.backtrace, example.metadata)
-                lines = [lines[0]] unless RSpec.configuration.full_cause_backtrace
+                lines = [lines[0]] unless RSpec.configuration.full_cause_backtrace # rubocop:disable Metrics/BlockNesting
 
                 lines.each do |line|
                   cause << ("  #{line}")