Update Gradle plugin version to rc4.

Change-Id: Ie37d29fd2e6e94f573b7284ec932021b7c2a75b9
(cherry picked from commit 29fd54cdf87e4e3fc22bb3c6cbcd1145506c863a)
diff --git a/base/version.gradle b/base/version.gradle
index 5657c62..123caa1 100644
--- a/base/version.gradle
+++ b/base/version.gradle
@@ -1,2 +1,2 @@
-project.ext.baseVersion = '23.2.7'
-project.ext.buildVersion = '1.0.0-rc3'
+project.ext.baseVersion = '23.2.8'
+project.ext.buildVersion = '1.0.0-rc4'