test(extend-app-start): Drop the no-op finishExtendedAppStart test

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: buenaflor

sentry-android-core/src/test/java/io/sentry/android/core/AppStartExtensionTest.kt

@@ -103,13 +103,6 @@ class AppStartExtensionTest {
     assertSame(span, ext.extendedAppStartSpan)
   }
 
-  @Test
-  fun `finishExtendedAppStart without a prior extend is a no-op`() {
-    val ext = extension()
-    ext.finishExtendedAppStart()
-    assertNull(ext.extendedEndTime)
-  }
-
   @Test
   fun `finishExtendedAppStart finishes the extended span`() {
     val ext = extension(windowOpen = true)