Bump version name to 2.8-rc-2

I realized only afterwards that I should have done this as part of
38fc206.

If it made sense in the merge commit to bump versionCode, because the
previous one had already been used with another versionName, then it
makes sense to bump versionName, too, because the previous one had
already been used with another versionCode.

Simplenote/build.gradle

@@ -30,7 +30,7 @@ android {
         if (project.hasProperty("versionName")) {
             versionName project.property("versionName")
         } else {
-            versionName "2.8-rc-1"
+            versionName "2.8-rc-2"
         }
         versionCode 109
         minSdkVersion 23