[ffigen] Fix global rename in README.md (#188)

pkgs/ffigen/README.md

diff --git a/pkgs/ffigen/README.md b/pkgs/ffigen/README.md
index 7c00f1a..9f516e4 100644
--- a/pkgs/ffigen/README.md
+++ b/pkgs/ffigen/README.md
@@ -179,7 +179,7 @@
     - aGlobal
   rename:
     # Removes '_' from beginning of a name.
-    - '_(.*)': '$1'
+    '_(.*)': '$1'
 ```
   </td>
   </tr>