Fix GitHub hosted runner README links

Author: domdomegg

content/actions/using-github-hosted-runners/about-github-hosted-runners.md

@@ -76,8 +76,8 @@ For more information, see "[Viewing workflow run history](/actions/managing-work
 
 For the overall list of included tools for each runner operating system, see the links below:
 
-* [Ubuntu 20.04 LTS](https://github.com/actions/virtual-environments/blob/main/images/linux/Ubuntu2004-README.md)
-* [Ubuntu 18.04 LTS](https://github.com/actions/virtual-environments/blob/main/images/linux/Ubuntu1804-README.md)
+* [Ubuntu 20.04 LTS](https://github.com/actions/virtual-environments/blob/main/images/linux/Ubuntu2004-Readme.md)
+* [Ubuntu 18.04 LTS](https://github.com/actions/virtual-environments/blob/main/images/linux/Ubuntu1804-Readme.md)
 * [Windows Server 2022](https://github.com/actions/virtual-environments/blob/main/images/win/Windows2022-Readme.md)
 * [Windows Server 2019](https://github.com/actions/virtual-environments/blob/main/images/win/Windows2019-Readme.md)
 * [Windows Server 2016](https://github.com/actions/virtual-environments/blob/main/images/win/Windows2016-Readme.md)