test(extend-app-start): Align NoOpAppStartExtenderTest with repo NoOp test idiom

Use the expression-body "does not throw" form for void no-op cases and drop
the getInstance singleton-identity test that no other NoOp test asserts.

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

Author: buenaflor

sentry/src/test/java/io/sentry/NoOpAppStartExtenderTest.kt

@@ -6,23 +6,12 @@ import kotlin.test.assertSame
 class NoOpAppStartExtenderTest {
   private val extender = NoOpAppStartExtender.getInstance()
 
-  @Test
-  fun `getInstance returns the same singleton`() {
-    assertSame(NoOpAppStartExtender.getInstance(), NoOpAppStartExtender.getInstance())
-  }
+  @Test fun `extendAppStart does not throw`() = extender.extendAppStart()
+
+  @Test fun `finishAppStart does not throw`() = extender.finishAppStart()
 
   @Test
   fun `getExtendedAppStartSpan returns NoOpSpan`() {
     assertSame(NoOpSpan.getInstance(), extender.extendedAppStartSpan)
   }
-
-  @Test
-  fun `extendAppStart is a no-op`() {
-    extender.extendAppStart()
-  }
-
-  @Test
-  fun `finishAppStart is a no-op`() {
-    extender.finishAppStart()
-  }
 }