Test: use shared Msal_Integration_tests UAMI in MI token acquirer E2E test (#3926)

Switch AcquireTokenWithManagedIdentity_UserAssignedAsync from the
Id4STesting managed identity (clientId 5bcd1685-...) to the consolidated
lab UAMI Msal_Integration_tests (clientId 45344e7d-...) in resource group
MSAL_MSI. This lets us retire the single-purpose Id4STesting identity and
reuse the shared lab identity already used by MSAL.NET E2E tests.

The test only acquires a token for the https://vault.azure.net audience,
so no Key Vault permissions are required; the new identity is a superset.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: RyAuld

tests/E2E Tests/TokenAcquirerTests/TokenAcquirer.cs

@@ -561,7 +561,9 @@ public async Task AcquireTokenWithManagedIdentity_UserAssignedAsync()
             // Arrange
             const string scope = "https://vault.azure.net/.default";
             const string baseUrl = "https://vault.azure.net";
-            const string clientId = "5bcd1685-b002-4fd1-8ebd-1ec3e1e4ca4d";
+            // User-assigned managed identity "Msal_Integration_tests" (RG MSAL_MSI, sub c1686c51-b717-4fe0-9af3-24a20a41fb0c).
+            // Shared/consolidated lab UAMI reused across MSAL and Id.Web E2E tests.
+            const string clientId = "45344e7d-c562-4be6-868f-18dac789c021";
             TokenAcquirerFactoryTesting.ResetTokenAcquirerFactoryInTest();
             TokenAcquirerFactory tokenAcquirerFactory = TokenAcquirerFactory.GetDefaultInstance();
             IServiceProvider serviceProvider = tokenAcquirerFactory.Build();