Fix OctoPrint logo in Readme

Fixed the broken link to the OctoPrint logo in the Readme under the Sources section. Now uses the logo present in the octoprint docs directory.

README.md

@@ -125,7 +125,7 @@ prompt and confirm by hitting ENTER.
 <tr>
 <th><img src="https://raw.githubusercontent.com/fluidd-core/fluidd/master/docs/assets/images/logo.svg" alt="Fluidd Logo" height="64"></th>
 <th><img src="https://avatars.githubusercontent.com/u/31575189?v=4" alt="jordanruthe avatar" height="64"></th>
-<th><img src="https://camo.githubusercontent.com/627be7fc67195b626b298af9b9677d7c58e698c67305e54324cffbe06130d4a4/68747470733a2f2f6f63746f7072696e742e6f72672f6173736574732f696d672f6c6f676f2e706e67" alt="OctoPrint Logo" height="64"></th>
+<th><img src="https://github.com/OctoPrint/OctoPrint/blob/a93b4d397248dc406a75e634c1326fb1b8ddcb63/docs/images/octoprint-logo.png" alt="OctoPrint Logo" height="64"></th>
 </tr>
 <tr>
 <th>by <a href="https://github.com/fluidd-core">fluidd-core</a></th>