Rename topic image to match convention

Author: glopesdev

topics/bonsai-rx/bonsai.png renamed to topics/bonsai-rx/bonsai-rx.png

@@ -2,7 +2,7 @@
 created_by: Goncalo Lopes
 display_name: Bonsai
 github_url: https://github.com/bonsai-rx/bonsai
-logo: bonsai.png
+logo: bonsai-rx.png
 related: language, dotnet
 released: November 2 2013
 short_description: Bonsai is a visual reactive programming language built on top of Rx.NET.