Fix Active Support failure for redis 4.2.0 with Ruby 2.8.0-dev

Gemfile.lock

@@ -386,7 +386,7 @@ GEM
       ffi (~> 1.0)
     rdoc (6.2.1)
     redcarpet (3.2.3)
-    redis (4.1.3)
+    redis (4.2.0)
     redis-namespace (1.7.0)
       redis (>= 3.0.4)
     regexp_parser (1.6.0)

activesupport/lib/active_support/cache/redis_cache_store.rb

@@ -398,7 +398,7 @@ module ActiveSupport
               modifiers[:nx] = unless_exist
               modifiers[:px] = (1000 * expires_in.to_f).ceil if expires_in
 
-              redis.with { |c| c.set key, serialized_entry, modifiers }
+              redis.with { |c| c.set key, serialized_entry, **modifiers }
             else
               redis.with { |c| c.set key, serialized_entry }
             end

activesupport/test/cache/stores/redis_cache_store_test.rb

@@ -290,7 +290,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
       @cache.redis.set("fu", "baz")
       @cache.clear
       assert_not @cache.exist?("foo")
-      assert @cache.redis.exists("fu")
+      assert @cache.redis.exists?("fu")
     end
 
     test "clear all cache key with Redis::Distributed" do