Drop api version from the BUCK build's manifest

The version number is not required, and only requires extra diligence
when bumping api versions. Hence, we drop it.

Change-Id: I803a617cbb92b0529dd818af6f04efe136f6fae3

BUCK

diff --git a/BUCK b/BUCK
index 980f082..760727e 100644
--- a/BUCK
+++ b/BUCK
@@ -18,7 +18,6 @@
   gwt_module = MODULE,
   manifest_entries = [
     'Gerrit-ApiType: plugin',
-    'Gerrit-ApiVersion: 2.12-SNAPSHOT',
     'Gerrit-HttpModule: com.googlesource.gerrit.plugins.xdocs.HttpModule',
     'Gerrit-Module: com.googlesource.gerrit.plugins.xdocs.Module',
     'Gerrit-InitStep: com.googlesource.gerrit.plugins.xdocs.XDocInit',