AWS Codebuild fails since buildspec is unable to install python version

My build fails, unable to install python 3.8, though python 3.8 is a supported runtime.

Reference:

https://docs.aws.amazon.com/codebuild/latest/userguide/runtime-versions.html
https://docs.aws.amazon.com/codebuild/latest/userguide/sample-runtime-versions.html

My build spec file:

 {
    "version": "0.2",
    "phases": {
      "install": {
        "runtime-versions": {
         "python": "3.8"
        }
      },
      "build": {
        "commands": [
          "cd lambda",
          "python -m pip install -r requirements.txt",
          "python -m pip install -r test/requirements.txt",
          "python -m unittest",
        ]
      }
    },
    "artifacts": {
      "files": "**/*"
    }
  }

Error:

[Container] 2023/07/06 11:54:17 Selecting 'python' runtime version '3.8' based on manual selections...
[Container] 2023/07/06 11:54:17 Phase complete: DOWNLOAD_SOURCE State: FAILED
[Container] 2023/07/06 11:54:17 Phase context status code: YAML_FILE_ERROR Message: Unknown runtime version named '3.8' of python. This build image has the following versions: 3.10

You should use Ubuntu Image Standard version 5.0. In Version 6, only Python 3.10 is supported, per documentation

To update it for the existing CodeBuild project, go to the CodeBuild project, click Edit button, and choose Environment. You will have a button on top saying Override image.
Under Image select aws/codebuild/standard:5.0
Then click on Update Environment at the bottom of the page