Remove LoginActivityAuthErrorTest — fragile Activity-based tests

Testing onAuthFlowError via ActivityScenario.launch couples to the
entire SDK initialization chain and uses Thread.sleep for timing.
The ViewModel-level tests in LoginViewModelMockTest adequately cover
the error propagation path without the fragility.

Author: JohnsonEricAtSalesforce

libs/test/SalesforceSDKTest/AndroidManifest.xml

@@ -19,12 +19,6 @@
         </service>
 
 
-
-        <!-- Test-only activity for LoginActivityAuthErrorTest -->
-        <activity android:name="com.salesforce.androidsdk.auth.TestLoginActivity"
-            android:exported="false"
-            android:theme="@style/SalesforceSDK" />
-
         <!-- Launcher screen -->
         <activity android:name="com.salesforce.androidsdk.MainActivity"
             android:label="@string/app_name"