gtk-engines: Update version from 2.20.1 to 2.20.2

From the [news file][1]:

> Overview of Changes in 2.20.2 (since 2.10.1)
> ============================================
>
> Changes in this release:
>  - Fix evolution ETree header in Clearlooks
>  - Minor fixes in mist
>  - Removed Xfce specific workaround from the clearlooks engine (bug #616124)

[1]: https://ftp.gnome.org/pub/gnome/sources/gtk-engines/2.20/gtk-engines-2.20.2.news

gtk-engines.be0

@@ -1,6 +1,6 @@
 #!/usr/bin/env beesh
 
-# BEE_VERSION gtk-engines-2.20.1-0
+# BEE_VERSION gtk-engines-2.20.2-0
 
 ## this file was created by bee init and should be executed to build a
 ## bee-package. (Additional hints are located at the end of this file.)