MM-53688 Remove boards dataretention (#24231)

* remove boards data-retention

* remove another variable

* update snapshots, to remove boards

* need to keep config settings until focalboard is updated

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/model/data_retention_policy.go

@@ -6,10 +6,8 @@ package model
 type GlobalRetentionPolicy struct {
 	MessageDeletionEnabled bool  `json:"message_deletion_enabled"`
 	FileDeletionEnabled    bool  `json:"file_deletion_enabled"`
-	BoardsDeletionEnabled  bool  `json:"boards_deletion_enabled"`
 	MessageRetentionCutoff int64 `json:"message_retention_cutoff"`
 	FileRetentionCutoff    int64 `json:"file_retention_cutoff"`
-	BoardsRetentionCutoff  int64 `json:"boards_retention_cutoff"`
 }
 
 type RetentionPolicy struct {