Use builtin bpfmt preupload check

Test: try and upload a commit with a badly formatted *.bp file
Exempt-From-Owner-Approval: preupload is broken
Change-Id: I24b41f03e5bee855e129d1e75fec2e737ae559d7

PREUPLOAD.cfg

diff --git a/PREUPLOAD.cfg b/PREUPLOAD.cfg
index 827f640..18b0a1b 100644
--- a/PREUPLOAD.cfg
+++ b/PREUPLOAD.cfg
@@ -1,10 +1,6 @@
 [Options]
 ignore_merged_commits = true
 
-# Ensure that bp files are correctly formatted.
-# Note: uses libcore's script.
-[Hook Scripts]
-bpfmt-check = ${REPO_ROOT}/libcore/tools/check-bpfmt.sh ${PREUPLOAD_COMMIT}
-
 [Builtin Hooks]
 clang_format = true
+bpfmt = true