[release/7.0] Stop building / testing on Ubuntu 18.04 (#43948)

- use 20.04 instead

.azure/pipelines/jobs/default-build.yml

@@ -109,7 +109,7 @@ jobs:
         vmImage: macOS-11
       ${{ if eq(parameters.agentOs, 'Linux') }}:
         ${{ if and(eq(parameters.useHostedUbuntu, true), or(ne(variables['System.TeamProject'], 'internal'), in(variables['Build.Reason'], 'Manual', 'PullRequest', 'Schedule'))) }}:
-          vmImage: ubuntu-18.04
+          vmImage: ubuntu-20.04
         ${{ if or(eq(parameters.useHostedUbuntu, false), and(eq(variables['System.TeamProject'], 'internal'), notin(variables['Build.Reason'], 'Manual', 'PullRequest', 'Schedule'))) }}:
           ${{ if eq(variables['System.TeamProject'], 'public') }}:
             name: NetCore-Svc-Public

eng/scripts/RunHelix.ps1

@@ -11,9 +11,7 @@
     Debian.11.Amd64.Open
     Mariner
     Redhat.7.Amd64.Open
-    Ubuntu.1804.Amd64.Open
     Ubuntu.2004.Amd64.Open
-    OSX.1015.Amd64.Open
     OSX.1100.Amd64.Open
     Windows.10.Amd64.Server20H2.Open
     Windows.11.Amd64.Client.Open

eng/targets/Helix.Common.props

@@ -1,11 +1,11 @@
 <Project>
   <!-- This file is shared between Helix.proj and .csproj files. -->
   <PropertyGroup>
-    <HelixQueueAlpine314>(Alpine.314.Amd64.Open)Ubuntu.18[email protected]/dotnet-buildtools/prereqs:alpine-3.14-helix-amd64-20210910135833-1848e19</HelixQueueAlpine314>
-    <HelixQueueDebian11>(Debian.11.Amd64.Open)Ubuntu.18[email protected]/dotnet-buildtools/prereqs:debian-11-helix-amd64-20211001171307-0ece9b3</HelixQueueDebian11>
-    <HelixQueueFedora34>(Fedora.34.Amd64.Open)Ubuntu.18[email protected]/dotnet-buildtools/prereqs:fedora-34-helix-20210924174119-4f64125</HelixQueueFedora34>
-    <HelixQueueMariner>(Mariner)Ubuntu.18[email protected]/dotnet-buildtools/prereqs:cbl-mariner-1.0-helix-20210528192219-92bf620</HelixQueueMariner>
-    <HelixQueueArmDebian11>(Debian.11.Arm64.Open)Ubuntu.18[email protected]/dotnet-buildtools/prereqs:debian-11-helix-arm64v8-20211001171229-97d8652</HelixQueueArmDebian11>
+    <HelixQueueAlpine314>(Alpine.314.Amd64.Open)Ubuntu.20[email protected]/dotnet-buildtools/prereqs:alpine-3.14-helix-amd64-20210910135833-1848e19</HelixQueueAlpine314>
+    <HelixQueueDebian11>(Debian.11.Amd64.Open)Ubuntu.20[email protected]/dotnet-buildtools/prereqs:debian-11-helix-amd64-20211001171307-0ece9b3</HelixQueueDebian11>
+    <HelixQueueFedora34>(Fedora.34.Amd64.Open)Ubuntu.20[email protected]/dotnet-buildtools/prereqs:fedora-34-helix-20210924174119-4f64125</HelixQueueFedora34>
+    <HelixQueueMariner>(Mariner)Ubuntu.20[email protected]/dotnet-buildtools/prereqs:cbl-mariner-1.0-helix-20210528192219-92bf620</HelixQueueMariner>
+    <HelixQueueArmDebian11>(Debian.11.Arm64.Open)Ubuntu.20[email protected]/dotnet-buildtools/prereqs:debian-11-helix-arm64v8-20211001171229-97d8652</HelixQueueArmDebian11>
 
     <!-- Do not attempt to override global property. -->
     <RunQuarantinedTests Condition=" '$(RunQuarantinedTests)' == '' ">false</RunQuarantinedTests>
@@ -27,7 +27,7 @@
       <!-- aspnetcore-ci[-official] (ci.yml) -->
       <!-- aspnetcore-quarantined-pr (quarantined-pr.yml) -->
       <ItemGroup>
-        <HelixAvailableTargetQueue Include="Ubuntu.1804.Amd64.Open" Platform="Linux" />
+        <HelixAvailableTargetQueue Include="Ubuntu.2004.Amd64.Open" Platform="Linux" />
         <HelixAvailableTargetQueue Include="OSX.1100.Amd64.Open" Platform="OSX" />
         <HelixAvailableTargetQueue Include="Windows.11.Amd64.Client.Open" Platform="Windows" />
       </ItemGroup>
@@ -38,7 +38,6 @@
       <ItemGroup>
         <!-- Linux -->
         <HelixAvailableTargetQueue Include="Redhat.7.Amd64.Open" Platform="Linux" />
-        <HelixAvailableTargetQueue Include="Ubuntu.2004.Amd64.Open" Platform="Linux" />
 
         <!-- Containers -->
         <HelixAvailableTargetQueue Include="$(HelixQueueAlpine314)" Platform="Linux" />