fix: Redis 6 on Heroku breaks ActionCable config (#4269)

Heroku made some SSL/TLS changes with Redis 6, which is breaking the ActionCable configuration.
Hence providing an environment variable configuration `REDIS_OPENSSL_VERIFY_MODE` to fix that.

set the value `none` for this environment variable in your Heroku installations where breakage occurs.

fixes: #2420

spec/lib/redis/config_spec.rb

@@ -16,7 +16,7 @@ describe ::Redis::Config do
 
     it 'checks for app redis config' do
       app_config = described_class.app
-      expect(app_config.keys).to match_array([:url, :password, :network_timeout, :reconnect_attempts])
+      expect(app_config.keys).to match_array([:url, :password, :network_timeout, :reconnect_attempts, :ssl_params])
       expect(app_config[:url]).to eq(redis_url)
       expect(app_config[:password]).to eq(redis_pasword)
     end
@@ -46,7 +46,7 @@ describe ::Redis::Config do
     end
 
     it 'checks for app redis config' do
-      expect(described_class.app.keys).to match_array([:url, :password, :sentinels, :network_timeout, :reconnect_attempts])
+      expect(described_class.app.keys).to match_array([:url, :password, :sentinels, :network_timeout, :reconnect_attempts, :ssl_params])
       expect(described_class.app[:url]).to eq("redis://#{redis_master_name}")
       expect(described_class.app[:sentinels]).to match_array(expected_sentinels)
     end