CI: Use 'ubuntu-latest' for GetReleaseVersion

Ubuntu is much faster than Windows at installing many small files,
such as during `git clone` and `npm install`.

Author: DeeDeeG

script/vsts/nightly-release.yml

@@ -1,7 +1,7 @@
 jobs:
   - job: GetReleaseVersion
     pool:
-      vmImage: 'windows-latest'
+      vmImage: 'ubuntu-latest'
     steps:
       # This has to be done separately because VSTS inexplicably
       # exits the script block after `npm install` completes.

script/vsts/pull-requests.yml

@@ -3,7 +3,7 @@ trigger: none # No CI builds, only PR builds
 jobs:
   - job: GetReleaseVersion
     pool:
-      vmImage: 'windows-latest'
+      vmImage: 'ubuntu-latest'
     steps:
       # This has to be done separately because VSTS inexplicably
       # exits the script block after `npm install` completes.

script/vsts/release-branch-build.yml

@@ -7,7 +7,7 @@ pr: none # no PR triggers
 jobs:
   - job: GetReleaseVersion
     pool:
-      vmImage: 'windows-latest'
+      vmImage: 'ubuntu-latest'
     steps:
       # This has to be done separately because VSTS inexplicably
       # exits the script block after `npm install` completes.
@@ -42,8 +42,6 @@ jobs:
       IsSignedZipBranch: $[ dependencies.GetReleaseVersion.outputs['Version.IsSignedZipBranch'] ]
 
     steps:
-      - template: platforms/templates/preparation.yml
-
       # This has to be done separately because VSTS inexplicably
       # exits the script block after `npm install` completes.
       - script: |