lightning: remove importer backend (pingcap#8421)

ecosystem-tool-user-guide.md

@@ -73,7 +73,7 @@ The following are the basics of TiDB Lightning:
 
 > **Note:**
 >
-> The Loader tool is no longer maintained. For scenarios related to Loader, it is recommended that you use the `tidb` mode of TiDB Lighting instead. For details, see [TiDB Lightning TiDB backends](/tidb-lightning/tidb-lightning-backends.md#migrating-from-loader-to-tidb-lightning-tidb-backend).
+> The Loader tool is no longer maintained. For scenarios related to Loader, it is recommended that you use TiDB-backend instead.
 
 ### Backup and restore
 

tidb-lightning/deploy-tidb-lightning.md

@@ -8,8 +8,6 @@ aliases: ['/docs/dev/tidb-lightning/deploy-tidb-lightning/','/docs/dev/reference
 
 This document describes the hardware requirements of TiDB Lightning using the Local-backend, and how to deploy it manually.
 
-If Local-backend is used for data import, during the import process, **the cluster cannot provide services**. If you do not want the TiDB services to be impacted, perform the data import according to [TiDB Lightning TiDB-backend](/tidb-lightning/tidb-lightning-backends.md#tidb-lightning-tidb-backend).
-
 ## Notes
 
 Before starting TiDB Lightning, note that:
@@ -69,7 +67,7 @@ You can find deployment instructions in [TiDB Quick Start Guide](/quick-start-wi
 
 #### Step 2: Download the TiDB Lightning installation package
 
-Refer to the [TiDB enterprise tools download page](/download-ecosystem-tools.md#tidb-lightning) to download the TiDB Lightning package. 
+Refer to the [TiDB enterprise tools download page](/download-ecosystem-tools.md#tidb-lightning) to download the TiDB Lightning package.
 
 > **Note:**
 >