docs: remove docs of kernel source tree

Author: mrdrivingduck

.github/workflows/docs-build.yml

@@ -1,6 +1,6 @@
 <div align="center">
 
-[![logo](./polar-doc/docs/.vuepress/public/images/polardb.png)](https://apsaradb.github.io/PolarDB-for-PostgreSQL/)
+[![logo](https://raw.githubusercontent.com/polardb/polardb-pg-docs/main/docs/.vuepress/public/images/polardb.png)](https://apsaradb.github.io/PolarDB-for-PostgreSQL/)
 
 # PolarDB for PostgreSQL
 
@@ -25,7 +25,7 @@
 
 ## Overview
 
-![arch.png](./polar-doc/docs/imgs/1_polardb_architecture.png)
+![arch.png](https://raw.githubusercontent.com/polardb/polardb-pg-docs/main/docs/imgs/1_polardb_architecture.png)
 
 PolarDB for PostgreSQL (hereafter simplified as PolarDB) is a cloud native database service independently developed by Alibaba Cloud. This service is 100% compatible with PostgreSQL and uses a shared-storage-based architecture in which computing is decoupled from storage. This service features flexible scalability, millisecond-level latency and hybrid transactional/analytical processing (HTAP) capabilities.
 

.github/workflows/docs-format-check.yml

@@ -1,6 +1,6 @@
 <div align="center">
 
-[![logo](./polar-doc/docs/.vuepress/public/images/polardb.png)](https://www.polardbpg.com/home)
+[![logo](https://raw.githubusercontent.com/polardb/polardb-pg-docs/main/docs/.vuepress/public/images/polardb.png)](https://apsaradb.github.io/PolarDB-for-PostgreSQL/)
 
 # PolarDB for PostgreSQL
 
@@ -25,7 +25,7 @@
 
 ## 什么是 PolarDB for PostgreSQL
 
-![arch.png](./polar-doc/docs/zh/imgs/1_polardb_architecture.png)
+![arch.png](https://raw.githubusercontent.com/polardb/polardb-pg-docs/main/docs/zh/imgs/1_polardb_architecture.png)
 
 PolarDB for PostgreSQL（下文简称为 PolarDB）是一款阿里云自主研发的云原生数据库，100% 兼容 PostgreSQL，采用基于 Shared-Storage 的存储计算分离架构，具有极致弹性、毫秒级延迟、HTAP 的能力。
 

README.md

@@ -3,7 +3,6 @@ This is not an introduction or user document for pg_repack, if you are looking f
 
 1. external/pg_repack/README.rst for a brief introduction of pg_repack.
 2. external/pg_repack/doc/pg_repack.rst for more details about Downloading, Installing, Execution and Release Notes.
-3. polar-doc/docs/zh/features/v11/extensions/pg-repack.md for PolarDB user document of pg_repack.
 
 Here we focus on how to develop new features by ourselves or port new features from the pg_repack community.