fix: emulator tests (apply @flaky)

`IgnoreFlakyTestsInCIRule` was not applied to the test class

So we apply the rule, and improve the documentation

AnkiDroid/src/androidTest/java/com/ichi2/anki/tests/InstrumentedTest.kt

@@ -33,6 +33,7 @@ import com.ichi2.libanki.Collection
 import com.ichi2.libanki.Consts
 import com.ichi2.libanki.Note
 import com.ichi2.libanki.utils.TimeManager
+import com.ichi2.testutils.IgnoreFlakyTestsInCIRule
 import kotlinx.coroutines.runBlocking
 import net.ankiweb.rsdroid.BackendException
 import org.junit.After
@@ -55,6 +56,10 @@ abstract class InstrumentedTest {
     @get:Rule
     val ensureAllFilesAccessRule = EnsureAllFilesAccessRule()
 
+    /** Allows [com.ichi2.testutils.Flaky] to annotate tests in subclasses */
+    @get:Rule
+    val ignoreFlakyTests = IgnoreFlakyTestsInCIRule()
+
     /**
      * @return A File object pointing to a directory in which temporary test files can be placed. The directory is
      * emptied on every invocation of this method so it is suitable to use at the start of each test.

testlib/src/main/java/com/ichi2/testutils/IgnoreFlakyTestsInCIRule.kt

@@ -30,6 +30,16 @@ import java.util.*
 
 /**
  * An annotation which marks a test as flaky so it will be skipped if run under CI
+ *
+ * The test class or a subclass must contain the code:
+ *
+ * ```kotlin
+ *     @get:Rule
+ *     val ignoreFlakyTests = IgnoreFlakyTestsInCIRule()
+ * ```
+ *
+ * @see IgnoreFlakyTestsInCIRule
+ *
  * @param os The OS The test fails under (required)
  * @param message The message to display when the test is skipped
  */