Refactor: Change Refinement To Understand That each Passes One Item

Why This Change Is Necessary
========================================================================

`each` does not deal with multiple items, it always yields [a single
element][2] and so we can refrain from using `args` there.

What These Changes Do To Address the Issue
========================================================================

Switch from `*args` to `item`.

Caveats
------------------------------------------------------------------------

We are still going to pass `*yielded_args` to the `yield` because in the
next commit we will pass a second argument to that `yield` call.

Side Effects Caused By This Change
========================================================================

None expected.

------------------------------------------------------------------------

**Relevant URLs:**

  * [Ticket Link][1]
  * [Ruby Doc For `each`][2]

------------------------------------------------------------------------

[1]: #185
[2]: https://ruby-doc.org/2.7.6/Enumerator.html#method-i-each

Author: jfelchner

lib/ruby-progressbar/refinements/enumerator.rb

@@ -5,11 +5,14 @@ module Enumerator
   def with_progressbar(options = {}, &block)
     progress_bar = ProgressBar.create(options.merge(:starting_at => 0, :total => size))
 
-    each do |*yielded_args|
+    each do |item|
       progress_bar.increment
 
       next unless block
 
+      yielded_args = []
+      yielded_args << item
+
       yield(*yielded_args)
     end
   end