Readme: replace header image for dark mode

- Fix text contrast for dark mode and dimmed mode with white outlines around the black text

fixes #8024

README.md

@@ -1,6 +1,6 @@
 # go-ipfs
 
-![banner](https://ipfs.io/ipfs/QmVk7srrwahXLNmcDYvyUEJptyoxpndnRa57YJ11L4jV26/ipfs.go.png)
+![banner](https://ipfs.io/ipfs/bafykbzacecaesuqmivkauix25v6i6xxxsvsrtxknhgb5zak3xxsg2nb4dhs2u/ipfs.go.png)
 
 [![](https://img.shields.io/badge/made%20by-Protocol%20Labs-blue.svg?style=flat-square)](http://ipn.io)
 [![Matrix](https://img.shields.io/badge/matrix-%23ipfs%3Amatrix.org-blue.svg?style=flat-square)](https://matrix.to/#/room/#ipfs:matrix.org)