Fix Synthetic accessor function lint errors on writeData.

Test: datastore:datastore-core:test
Bug: 157173926
Change-Id: I46fbae4730f897876dfb06c153b9c09be207a936
diff --git a/datastore/datastore-core/src/main/kotlin/androidx/datastore/SingleProcessDataStore.kt b/datastore/datastore-core/src/main/kotlin/androidx/datastore/SingleProcessDataStore.kt
index 3e5a0ae..b0600c9 100644
--- a/datastore/datastore-core/src/main/kotlin/androidx/datastore/SingleProcessDataStore.kt
+++ b/datastore/datastore-core/src/main/kotlin/androidx/datastore/SingleProcessDataStore.kt
@@ -270,7 +270,11 @@
         }
     }
 
-    private fun writeData(newData: T) {
+    /**
+     * Internal only to prevent creation of synthetic accessor function. Do not call this from
+     * outside this class.
+     */
+    internal fun writeData(newData: T) {
         file.createParentDirectories()
 
         val scratchFile = File(file.absolutePath + SCRATCH_SUFFIX)