rn-61: use images inside the repo

Author: chriscool

images/git_merge_2020_cake.jpg

@@ -30,11 +30,11 @@ This edition covers what happened during the month of February 2020.
  had to be changed at the last minute due to coronavirus related
  reasons.
 
- On the wall [a big timeline](https://photos.google.com/share/AF1QipP764-lYtgUakk-4Kr_Njh6S3GZE0BqdU8V_3j63RyhTygxNR12oO3mY5gSJdSGGA/photo/AF1QipPDidUvdLbTsS9DJKJlAVQ-PEV5zP1MZ4NIkd-x)
+ On the wall [a big timeline](images/git_merge_2020_timeline.jpg)
  mentioned some important events in Git history.
 
  There was a party in the evening with
-[a big cake dedicated to Git's 15th anniversary](https://photos.google.com/share/AF1QipP764-lYtgUakk-4Kr_Njh6S3GZE0BqdU8V_3j63RyhTygxNR12oO3mY5gSJdSGGA/photo/AF1QipOXskul_osttaPQuOHkR1wAQQdOJb4j89VO3ipn).
+[a big cake dedicated to Git's 15th anniversary](images/git_merge_2020_cake.jpg).
 
 *[Git Contributor Summit](https://lore.kernel.org/git/[email protected]/)
 
@@ -250,4 +250,4 @@ Christian Couder &lt;<[email protected]>&gt;,
 Jakub Narębski &lt;<[email protected]>&gt;,
 Markus Jansen &lt;<[email protected]>&gt; and
 Kaartic Sivaraam &lt;<[email protected]>&gt;
-with help from Jiang Xin.
+with help from Jiang Xin and Nuritzi Sanchez.