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
