DEV: Fix various rubocop lints (#24749)
These (21 + 3 from previous PRs) are soon to be enabled in rubocop-discourse:
Capybara/VisibilityMatcher
Lint/DeprecatedOpenSSLConstant
Lint/DisjunctiveAssignmentInConstructor
Lint/EmptyConditionalBody
Lint/EmptyEnsure
Lint/LiteralInInterpolation
Lint/NonLocalExitFromIterator
Lint/ParenthesesAsGroupedExpression
Lint/RedundantCopDisableDirective
Lint/RedundantRequireStatement
Lint/RedundantSafeNavigation
Lint/RedundantStringCoercion
Lint/RedundantWithIndex
Lint/RedundantWithObject
Lint/SafeNavigationChain
Lint/SafeNavigationConsistency
Lint/SelfAssignment
Lint/UnreachableCode
Lint/UselessMethodDefinition
Lint/Void
Previous PRs:
Lint/ShadowedArgument
Lint/DuplicateMethods
Lint/BooleanSymbol
RSpec/SpecFilePathSuffix
694b5f108b