Bump API_LEVEL so we can use androidx prebuilts

Test: presubmit
Bug: 228469190
Change-Id: I4259a8ba2720c0c92b4eb6913ce20e14fa289ad3
diff --git a/src/test/java/com/android/tools/metalava/DriverTest.kt b/src/test/java/com/android/tools/metalava/DriverTest.kt
index 7d8bb88..b8f2f85 100644
--- a/src/test/java/com/android/tools/metalava/DriverTest.kt
+++ b/src/test/java/com/android/tools/metalava/DriverTest.kt
@@ -1340,7 +1340,7 @@
     }
 
     companion object {
-        private const val API_LEVEL = 30
+        private const val API_LEVEL = 31
 
         private fun getAndroidJarFromEnv(apiLevel: Int): File {
             val sdkRoot = System.getenv("ANDROID_SDK_ROOT")