`azuredevops_repository_policy_max_file_size` Add max file size 50M

[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: #1162

=== RUN   TestAccRepositoryPolicyFileSize
=== RUN   TestAccRepositoryPolicyFileSize/RepositoryPolicies
=== RUN   TestAccRepositoryPolicyFileSize/RepositoryPolicies/basic
=== RUN   TestAccRepositoryPolicyFileSize/RepositoryPolicies/update
=== PAUSE TestAccRepositoryPolicyFileSize/RepositoryPolicies/update
=== CONT  TestAccRepositoryPolicyFileSize/RepositoryPolicies/update
=== RUN   TestAccRepositoryPolicyFileSize/ProjectPolicies
=== RUN   TestAccRepositoryPolicyFileSize/ProjectPolicies/basic
=== RUN   TestAccRepositoryPolicyFileSize/ProjectPolicies/update
=== PAUSE TestAccRepositoryPolicyFileSize/ProjectPolicies/update
=== CONT  TestAccRepositoryPolicyFileSize/ProjectPolicies/update
--- PASS: TestAccRepositoryPolicyFileSize (251.83s)
    --- PASS: TestAccRepositoryPolicyFileSize/RepositoryPolicies (60.52s)
        --- PASS: TestAccRepositoryPolicyFileSize/RepositoryPolicies/basic (60.52s)
        --- PASS: TestAccRepositoryPolicyFileSize/RepositoryPolicies/update (67.17s)
    --- PASS: TestAccRepositoryPolicyFileSize/ProjectPolicies (55.07s)
        --- PASS: TestAccRepositoryPolicyFileSize/ProjectPolicies/basic (55.07s)
        --- PASS: TestAccRepositoryPolicyFileSize/ProjectPolicies/update (69.07s)
PASS
ok      github.com/microsoft/terraform-provider-azuredevops/azuredevops/internal/acceptancetests        257.416s

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

• [ ] Yes
• [x] No

Does this introduce a breaking change?

• [ ] Yes
• [x] No

Any relevant logs, error output, etc?

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