Fix og:image path

Author: jkseppan

index.html

@@ -18,7 +18,7 @@
   <meta name="description" content="A group of Python and data enthusiasts in Helsinki, Finland">
   <meta property="og:description" content="A group of Python and data enthusiasts in Helsinki, Finland">
   <meta property="og:type" content="website">
-  <meta property="og:image" content="/assets/PyData_Meetup_Logo_Template_-_Helsinki.png">
+  <meta property="og:image" content="https://pydata-helsinki.github.io/assets/PyData_Meetup_Logo_Template_-_Helsinki.png">
   <meta property="og:image:alt" content="PyData Helsinki logo">
   <meta property="og:image:width" content="200">
   <meta property="og:image:height" content="203">