[Bug]:Fix ObsoleteReason of Subcontracting Feature Flag Codeunit

Describe the issue

The ObsoleteReason of the feature flag codeunit states that Legacy Subcontracting will be discontinued and that environments should move to the Subcontracting App. This wording implies that the codeunit primarily supports the legacy solution and is being removed because the legacy functionality is being deprecated.

Expected behavior

The ObsoleteReason should clearly state that the codeunit exists as a temporary migration and transition mechanism that enables customers to move from Legacy Subcontracting to the Subcontracting App. The removal should be tied to the completion of the migration and the cleanup of the remaining legacy artifacts.

Steps to reproduce

Open the Codeunit
Read the Obsoletion Text

Additional context

##Impact

The current message can mislead developers and maintainers regarding the purpose of the codeunit and the rationale behind its obsoletion. This may cause confusion when reviewing deprecation warnings or planning migration activities.

##Proposed Fix

Update the ObsoleteReason text to describe the codeunit as a temporary migration guard and indicate that it will be removed once the Legacy Subcontracting field and related conditional compilation code have been removed.

ObsoleteReason = 'This codeunit is a temporary transition guard for the migration from Legacy Subcontracting to the Subcontracting App. It will be removed once the Legacy Subcontracting field and all related conditional compilation blocks are cleaned up.';

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