Updates date range joiner

Why are these changes being introduced:

* Some date ranges ended up looking like `1999-01-01-1999-01-02` with
  the current previous logic which is confusing.

Relevant ticket(s):

* https://mitlibraries.atlassian.net/browse/USE-296

How does this address that need:

* Changes our joiner from `-` to ` to ` for date ranges.

Author: JPrevost

app/models/normalize_timdex_record.rb

@@ -182,7 +182,7 @@ def date_range
     # first.
     relevant_date = relevant_dates.first
 
-    "#{relevant_date['range']['gte']}-#{relevant_date['range']['lte']}"
+    "#{relevant_date['range']['gte']} to #{relevant_date['range']['lte']}"
   end
 
   def contributors

test/models/normalize_timdex_record_test.rb

@@ -82,7 +82,7 @@ def minimal_record
       { 'kind' => 'creation', 'range' => { 'lte' => '2023', 'gte' => '2020' } }
     ]
     normalized = NormalizeTimdexRecord.new(record, 'test').normalize
-    assert_equal '2020-2023', normalized[:date_range]
+    assert_equal '2020 to 2023', normalized[:date_range]
   end
 
   test 'normalizes format from content type' do