[March 17] Remove all notes about ubuntu-latest migration and fix labels (#18243)

Co-authored-by: Sarah Edwards <skedwards88@github.com>

Author: AlenaSviridenko

content/actions/reference/workflow-syntax-for-github-actions.md

@@ -314,7 +314,6 @@ Available {% data variables.product.prodname_dotcom %}-hosted runner types are:
 
 {% data reusables.github-actions.supported-github-runners %}
 
-{% data reusables.github-actions.ubuntu-runner-preview %}
 {% data reusables.github-actions.macos-runner-preview %}
 
 ##### Example

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

@@ -55,7 +55,6 @@ Hardware specification for macOS virtual machines:
 
 {% data reusables.github-actions.supported-github-runners %}
 
-{% data reusables.github-actions.ubuntu-runner-preview %}
 {% data reusables.github-actions.macos-runner-preview %}
 
 Workflow logs list the runner used to run a job. For more information, see "[Viewing workflow run history](/actions/managing-workflow-runs/viewing-workflow-run-history)."

data/reusables/github-actions/supported-github-runners.md

@@ -1,8 +1,8 @@
 | Virtual environment | YAML workflow label |
 | --------------------|---------------------|
 | Windows Server 2019 | `windows-latest` or `windows-2019` |
-| Ubuntu 20.04 | `ubuntu-latest` (see note) or `ubuntu-20.04` |
-| Ubuntu 18.04 | `ubuntu-latest` (see note) or `ubuntu-18.04` |
+| Ubuntu 20.04 | `ubuntu-latest` or `ubuntu-20.04` |
+| Ubuntu 18.04 | `ubuntu-18.04` |
 | Ubuntu 16.04 | `ubuntu-16.04` |
 | macOS Big Sur 11.0 | `macos-11.0` |
 | macOS Catalina 10.15 | `macos-latest` or `macos-10.15` |