docs: fix broken anchors in BUILDING.md and README.md

Signed-off-by: Vincent <1729065730@qq.com>

BUILDING.md

@@ -4,7 +4,7 @@ This guide is useful if you intend to contribute on containerd. Thanks for your
 effort. Every contribution is very appreciated.
 
 This doc includes:
-* [Getting started with GitHub Codespaces](#getting-started-with-gitHub-codespaces)
+* [Getting started with GitHub Codespaces](#getting-started-with-github-codespaces)
 * [Build requirements](#build-requirements)
 * [Build the development environment](#build-the-development-environment)
 * [Build containerd](#build-containerd)

README.md

@@ -74,7 +74,7 @@ require the btrfs kernel module and btrfs tools to be installed on your Linux
 distribution.
 
 To use Linux checkpoint and restore features, you will need `criu` installed on
-your system. See more details in [Checkpoint and Restore](#checkpoint-and-restore).
+your system.
 
 Build requirements for developers are listed in [BUILDING](BUILDING.md).