Remove dangling reference to preload.bzl file (facebook#41634)

Summary:

# Changelog:
[Internal]-

The actual file was removed in facebook#36900, but the reference still remains, confusing different tools.

Reviewed By: sammy-SC

Differential Revision: D51559281

.buckconfig

@@ -15,6 +15,3 @@
 
 [alias]
   rntester = //packages/rn-tester/android/app:app
-
-[buildfile]
-  includes = //tools/build_defs/oss/preload.bzl