Remove flatbuffer's *_generated.h files from runfiles

All the `*_generated.h` files are currently ending up as runfiles.
They are truly unnecessary.

Binaries with a larger number of flatbuffer dependencies have a larger
number of headers in their runfiles.

I encountered this while trying to migrate rules_docker targets to
rules_oci. Looking at the container contents before/after showed these
superfluous files.

Change-Id: I5db02ded6ce38eb5329aecbc4fecd3dda013ba77
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/third_party/flatbuffers/build_defs.bzl b/third_party/flatbuffers/build_defs.bzl
index 5f6d71b..da26cec 100644
--- a/third_party/flatbuffers/build_defs.bzl
+++ b/third_party/flatbuffers/build_defs.bzl
@@ -96,7 +96,7 @@
         mnemonic = "Flatc",
         progress_message = "Generating flatbuffer files for %{input}:",
     )
-    return [DefaultInfo(files = depset(outs), runfiles = ctx.runfiles(files = outs)), FlatbufferLibraryInfo(srcs = ctx.files.srcs)]
+    return [DefaultInfo(files = depset(outs)), FlatbufferLibraryInfo(srcs = ctx.files.srcs)]
 
 _flatbuffer_library_compile = rule(
     implementation = _flatbuffer_library_compile_impl,