Update generate-v1.0-models.yml for Azure Pipelines (#209)

Same issue as microsoftgraph/msgraph-metadata#42

Author: MIchaelMainer

.azure-pipelines/generate-v1.0-models.yml

@@ -68,6 +68,7 @@ steps:
     targetType: inline
     workingDirectory: '$(Build.SourcesDirectory)/msgraph-typescript-typings'
     script: |
+      git fetch origin master | Write-Host
       git checkout master | Write-Host
 
 - task: PowerShell@2