remove last_successful_update, ignore error

most of the time we dont even check this error and checking
the string for particular errors is very flake as different
databases (sqlite and psql) use different error messages, and
some users might have it in other languages.

Fixes #1956

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

hscontrol/db/db.go

@@ -92,7 +92,7 @@ func NewHeadscaleDatabase(
 						RenameColumn(&types.Node{}, "nickname", "given_name")
 
 					dbConn.Model(&types.Node{}).Where("auth_key_id = ?", 0).Update("auth_key_id", nil)
-	// If the Node table has a column for registered,
+					// If the Node table has a column for registered,
 					// find all occourences of "false" and drop them. Then
 					// remove the column.
 					if tx.Migrator().HasColumn(&types.Node{}, "registered") {
@@ -319,14 +319,7 @@ func NewHeadscaleDatabase(
 				// no longer used.
 				ID: "202402151347",
 				Migrate: func(tx *gorm.DB) error {
-					err := tx.Migrator().DropColumn(&types.Node{}, "last_successful_update")
-					if err != nil && strings.Contains(err.Error(), `of relation "nodes" does not exist`) {
-						return nil
-					} else {
-						return err
-					}
-
-					return err
+					_ = tx.Migrator().DropColumn(&types.Node{}, "last_successful_update")
 				},
 				Rollback: func(tx *gorm.DB) error {
 					return nil