Prepare tools/r8_release.py for branch 8.10

Change-Id: Ib15897956886f5606a436e6c5c4483f0ffff24f7

tools/r8_release.py

diff --git a/tools/r8_release.py b/tools/r8_release.py
index 6abbf63..c288c96 100755
--- a/tools/r8_release.py
+++ b/tools/r8_release.py
@@ -17,7 +17,7 @@
 
 import utils
 
-R8_DEV_BRANCH = '8.9'
+R8_DEV_BRANCH = '8.10'
 R8_VERSION_FILE = os.path.join('src', 'main', 'java', 'com', 'android', 'tools',
                                'r8', 'Version.java')
 THIS_FILE_RELATIVE = os.path.join('tools', 'r8_release.py')