libc: fix kernel cleanup script typo.

Change-Id: I5fc119be535ed47dadc780234665335efa6b9ac5
diff --git a/libc/kernel/tools/defaults.py b/libc/kernel/tools/defaults.py
index ca7e6bb..5e9d6770 100644
--- a/libc/kernel/tools/defaults.py
+++ b/libc/kernel/tools/defaults.py
@@ -45,7 +45,7 @@
 
 # Replace tokens in the output according to this mapping
 kernel_token_replacements = {
-    {"asm": "__asm__"},
+    "asm": "__asm__",
     }
 
 # this is the set of known static inline functions that we want to keep