Make link_list compatible with Ruby 3 keyword args

We were using an optional parameter followed by keyword parameters,
which caused a warning with Ruby 2.7:

```
app/components/shared/link_list_component.rb:20: warning: Using the last
argument as keyword parameters is deprecated; maybe ** should be added
to the call
```

I've tried to make `current:` a named parameter as well and then change
all method calls to `link_list`, but was still getting the same warning.
Might have something to do with the fact that we're dealing with arrays
with hashes inside them instead of passing the keyword arguments
directly to the method.

app/components/shared/link_list_component.rb

@@ -17,7 +17,15 @@ class Shared::LinkListComponent < ApplicationComponent
     end
 
     def list_items
-      present_links.map do |text, url, current = false, **link_options|
+      present_links.map do |text, url, current_or_options = false, options = {}|
+        if current_or_options.is_a?(Hash)
+          current = false
+          link_options = current_or_options
+        else
+          current = current_or_options
+          link_options = options
+        end
+
         tag.li("aria-current": (true if current)) do
           if url
             link_to text, url, link_options