Rename blame-cache lib target to 'blame-cache'

The name is currently 'lib' which results in 'liblib.jar' being
generated.

Change it so the generated file is 'libblame-cache' which is more
meaningful.

Change-Id: I5f735b0b85592b883a14dadbb0c63be7f8014fe4

gitiles-servlet/BUILD

diff --git a/gitiles-servlet/BUILD b/gitiles-servlet/BUILD
index 127608b..aeb013d 100644
--- a/gitiles-servlet/BUILD
+++ b/gitiles-servlet/BUILD
@@ -4,7 +4,7 @@
 )
 
 DEPS = [
-    "//blame-cache:lib",
+    "//blame-cache:blame-cache",
     "//lib:autolink",
     "//lib:commons-lang",
     "//lib:gson",