Fluentd pods are crashing after upgrading OpenShift Logging to 5.2.4-17

Issue

• After successfully upgrading OpenShift Logging 5.2.x to 5.2.4-17 all fluentd pods are crashing.

  $ oc logs -f fluentd-ldd9b fluentd
  Setting each total_size_limit for 4 buffers to 4811272243 bytes
  Setting queued_chunks_limit_size for each buffer to 573
  Setting chunk_limit_size for each buffer to 8388608
  2021-12-28 15:32:41 +0000 [warn]: '@' is the system reserved prefix. It works in the nested configuration for now but it will be rejected: @timestamp
  2021-12-28 15:32:42 +0000 [error]: config error file="/etc/fluent/fluent.conf" error_class=Fluent::ConfigError error="Unknown formatter plugin 'single_json_value'. Run 'gem search -rd fluent-plugin' to find plugins"