v8.4: update CentOS 7-related descriptions (pingcap#19430)

Author: Oreoxmt

develop/dev-guide-build-cluster-in-cloud.md

@@ -108,10 +108,10 @@ mysql  Ver 8.0.28 for macos12.0 on arm64 (Homebrew)
 
 <div label="Linux">
 
-For Linux, the following takes CentOS 7 as an example:
+For Linux, the following takes Ubuntu as an example:
 
 ```shell
-yum install mysql
+apt-get install mysql-client
 ```
 
 Then, verify that the MySQL client is installed successfully:

hardware-and-software-requirements.md

@@ -31,7 +31,7 @@ As an open-source distributed SQL database with high performance, TiDB can be de
     <td><ul><li>x86_64</li><li>ARM 64</li></ul></td>
   </tr>
   <tr>
-    <td><ul><li>Red Hat Enterprise Linux 7.3 or a later 7.x version</li><li>CentOS 7.3 or a later 7.x version</li></ul></td>
+    <td>Red Hat Enterprise Linux 7.3 or a later 7.x version</td>
     <td><ul><li>x86_64</li><li>ARM 64</li></ul></td>
   </tr>
   <tr>
@@ -96,7 +96,7 @@ As an open-source distributed SQL database with high performance, TiDB can be de
 > **Note:**
 >
 > - For Oracle Enterprise Linux, TiDB supports the Red Hat Compatible Kernel (RHCK) and does not support the Unbreakable Enterprise Kernel provided by Oracle Enterprise Linux.
-> - According to [CentOS Linux EOL](https://www.centos.org/centos-linux-eol/), the upstream support for CentOS Linux 8 ended on December 31, 2021. CentOS Stream 8 continues to be supported by the CentOS organization.
+> - According to [CentOS Linux EOL](https://www.centos.org/centos-linux-eol/), the upstream support for CentOS Linux 7 ends on June 30, 2024. TiDB ends the support for CentOS 7 starting from the 8.4 DMR version. It is recommended to use Rocky Linux 9.1 or a later version. While the upstream support for CentOS Linux 8 ends on December 31, 2021, CentOS Stream 8 continues to be supported by the CentOS organization.
 > - Support for Ubuntu 16.04 will be removed in future versions of TiDB. Upgrading to Ubuntu 18.04 or later is strongly recommended.
 > - If you are using the 32-bit version of an operating system listed in the preceding table, TiDB **is not guaranteed** to be compilable, buildable or deployable on the 32-bit operating system and the corresponding CPU architecture, or TiDB does not actively adapt to the 32-bit operating system.
 > - Other operating system versions not mentioned above might work but are not officially supported.

ticdc/deploy-ticdc.md

@@ -9,12 +9,7 @@ This document describes how to deploy and maintain a TiCDC cluster, including th
 
 ## Software and hardware recommendations
 
-In production environments, the recommendations of software and hardware for TiCDC are as follows:
-
-| Linux OS       | Version         |
-| :----------------------- | :----------: |
-| Red Hat Enterprise Linux | 7.3 or later versions   |
-| CentOS                   | 7.3 or later versions   |
+In production environments, the recommendations of hardware for TiCDC are as follows:
 
 | CPU | Memory | Disk | Network | Number of TiCDC cluster instances (minimum requirements for production environment) |
 | :--- | :--- | :--- | :--- | :--- |