Update vendored Molinillo to 0.5.4

lib/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 module Gem::Resolver::Molinillo
   # The version of Gem::Resolver::Molinillo.
-  VERSION = '0.5.3'.freeze
+  VERSION = '0.5.4'.freeze
 end

lib/rubygems/resolver/molinillo/lib/molinillo/resolution.rb

@@ -194,18 +194,20 @@ def unwind_for_conflict
       def state_index_for_unwind
         current_requirement = requirement
         existing_requirement = requirement_for_existing_name(name)
-        until current_requirement.nil?
-          current_state = find_state_for(current_requirement)
-          return states.index(current_state) if state_any?(current_state)
-          current_requirement = parent_of(current_requirement)
+        index = -1
+        [current_requirement, existing_requirement].each do |r|
+          until r.nil?
+            current_state = find_state_for(r)
+            if state_any?(current_state)
+              current_index = states.index(current_state)
+              index = current_index if current_index > index
+              break
+            end
+            r = parent_of(r)
+          end
         end
 
-        until existing_requirement.nil?
-          existing_state = find_state_for(existing_requirement)
-          return states.index(existing_state) if state_any?(existing_state)
-          existing_requirement = parent_of(existing_requirement)
-        end
-        -1
+        index
       end
 
       # @return [Object] the requirement that led to `requirement` being added
@@ -376,7 +378,6 @@ def fixup_swapped_children(vertex)
             activated.delete_edge(outgoing_edge)
             requirements.delete(outgoing_edge.requirement)
           end
-          matching_deps.delete(outgoing_edge.requirement)
         end
       end