Enable Style/IdenticalConditionalBranches Rubocop cop

## What does this MR do?

This MR enables Rubocop cop that checks for identical lines at the end of each branch of a conditional statement.

Examples:

```ruby
@bad
if condition
  do_x
  do_z
else
  do_y
  do_z
end

@good
if condition
  do_x
else
  do_y
end
do_z
```

## What are the relevant issue numbers?

#17478

See merge request !5011