[Codacy] Change this constant to a 'static' read-only property.

[github-actions]

Codacy finding

• Repository: TransactionProcessing/SupportTools
• Codacy org: TransactionProcessing
• Codacy repo: SupportTools
• Codacy issue ID: ce990c20c04d5835b0f6cc40a667f22
• Codacy issue: https://app.codacy.com/gh/TransactionProcessing/SupportTools/issues/ce990c20c04d5835b0f6cc40a667f22
• File: TransactionProcessing.MerchantFileProcessor/Services/FileStatusStore.cs
• Line: 74
• Rule: SonarCSharp_S2339
• Severity: Warning

Message: Change this constant to a 'static' read-only property.

Sync metadata

Sync key: TransactionProcessing/SupportTools::TransactionProcessing/SupportTools::ce990c20c04d5835b0f6cc40a667f22