Add missing slf4j dependency in BUCK file for jgit-lfs-server

Change-Id: I0c7fcae123f94ebd8e5eb2700e3d601a1b199be9
Signed-off-by: Zhen Chen <czhen@google.com>
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.lfs.server/BUCK

@@ -11,7 +11,8 @@ java_library(
     '//org.eclipse.jgit.lfs:jgit-lfs',
     '//lib:gson',
     '//lib:httpcore',
-    '//lib:servlet-api'
+    '//lib:servlet-api',
+    '//lib:slf4j-api'
   ],
   visibility = ['PUBLIC'],
 )