Reland "Remove the return type from the syscall lists and parser."

It's not used, so it's just noise.

The previous attempt missed the call to grep in the .bp file that also
needed to be updated.

Bug: http://b/395691391
Bug: http://b/395732439
Change-Id: Ia0cc2e1882280e87a569acbaace9d84e753aad80
diff --git a/libc/SECCOMP_ALLOWLIST_SYSTEM.TXT b/libc/SECCOMP_ALLOWLIST_SYSTEM.TXT
index 756affe..ac90aac 100644
--- a/libc/SECCOMP_ALLOWLIST_SYSTEM.TXT
+++ b/libc/SECCOMP_ALLOWLIST_SYSTEM.TXT
@@ -3,4 +3,4 @@
 #
 # This file is processed by a python script named genseccomp.py.
 
-int bpf(int cmd, union bpf_attr *attr, unsigned int size) all
+bpf(int cmd, union bpf_attr *attr, unsigned int size) all