test: close DB in TimelineDaoTest (#512)

The previous code forgot to close the DB after TimelineDaoTest was run,
so a warning message was displayed when the test was run locally.

Close the database using the `@After` annotation.

Fixes #511

core/database/src/test/kotlin/app/pachli/core/database/dao/TimelineDaoTest.kt

@@ -28,6 +28,7 @@ import dagger.hilt.android.testing.HiltAndroidRule
 import dagger.hilt.android.testing.HiltAndroidTest
 import javax.inject.Inject
 import kotlinx.coroutines.runBlocking
+import org.junit.After
 import org.junit.Assert.assertEquals
 import org.junit.Before
 import org.junit.Rule
@@ -51,6 +52,11 @@ class TimelineDaoTest {
         hilt.inject()
     }
 
+    @After
+    fun tearDown() {
+        db.close()
+    }
+
     @Test
     fun insertGetStatus() = runBlocking {
         val setOne = makeStatus(statusId = 3)