[Bug fix] - `azuredevops_git_repository` - Fix plan fails when repo deleted outside of Terraform

[xuzhang3]

All Submissions:

• [x] Have you added an explanation of what your changes do and why you'd like us to include them?
• [x] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] My code follows the code style of this project.
• [x] I ran lint checks locally prior to submission.
• [x] Have you checked to ensure there aren't other open PRs for the same update/change?

What about the current behavior has changed?

Issue Number: #1086

=== RUN   TestAccGitRepo_CreateAndUpdate
=== PAUSE TestAccGitRepo_CreateAndUpdate
=== RUN   TestAccGitRepo_Create_IncorrectInitialization
=== PAUSE TestAccGitRepo_Create_IncorrectInitialization
=== RUN   TestAccGitRepo_Create_Import
=== PAUSE TestAccGitRepo_Create_Import
=== RUN   TestAccGitRepo_RepoInitialization_Clean
=== PAUSE TestAccGitRepo_RepoInitialization_Clean
=== RUN   TestAccGitRepo_RepoInitialization_Uninitialized
=== PAUSE TestAccGitRepo_RepoInitialization_Uninitialized
=== RUN   TestAccGitRepo_RepoFork_BranchNotEmpty
=== PAUSE TestAccGitRepo_RepoFork_BranchNotEmpty
=== RUN   TestAccGitRepo_PrivateImport_BranchNotEmpty
=== PAUSE TestAccGitRepo_PrivateImport_BranchNotEmpty
=== CONT  TestAccGitRepo_CreateAndUpdate
=== CONT  TestAccGitRepo_RepoInitialization_Uninitialized
=== CONT  TestAccGitRepo_Create_Import
=== CONT  TestAccGitRepo_Create_IncorrectInitialization
=== CONT  TestAccGitRepo_RepoInitialization_Clean
=== CONT  TestAccGitRepo_PrivateImport_BranchNotEmpty
=== CONT  TestAccGitRepo_RepoFork_BranchNotEmpty
--- PASS: TestAccGitRepo_Create_IncorrectInitialization (5.06s)
=== NAME  TestAccGitRepo_PrivateImport_BranchNotEmpty
    resource_git_repository_test.go:210: Step 1/1 error: Error running apply: exit status 1

        Error: Error import repository in Azure DevOps: Request returned status: 400 Bad Request

          with azuredevops_git_repository.import,
          on terraform_plugin_test.tf line 26, in resource "azuredevops_git_repository" "import":
          26:   resource "azuredevops_git_repository" "import" {

--- PASS: TestAccGitRepo_RepoInitialization_Uninitialized (61.00s)
--- PASS: TestAccGitRepo_RepoInitialization_Clean (62.29s)
--- PASS: TestAccGitRepo_RepoFork_BranchNotEmpty (65.21s)
--- FAIL: TestAccGitRepo_PrivateImport_BranchNotEmpty (75.26s)
--- PASS: TestAccGitRepo_Create_Import (87.40s)
--- PASS: TestAccGitRepo_CreateAndUpdate (102.15s)
FAIL
FAIL    github.com/microsoft/terraform-provider-azuredevops/azuredevops/internal/acceptancetests        102.786s
FAIL

Does this introduce a change to go.mod, go.sum or vendor/?

• [x] Yes
• [ ] No

Does this introduce a breaking change?

• [x] Yes
• [ ] No

Any relevant logs, error output, etc?

(If it’s long, please paste to https://ghostbin.com/ and insert the link here.)

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