update the readme hash in sharness

test/sharness/lib/test-lib-hashes.sh

 # this file defines several useful hashes used across the test codebase.
 # thus they can be defined + changed in one place
 
-HASH_WELCOME_DOCS="QmPXME1oRtoT627YKaDPDQ3PwA8tdP9rWuAAweLzqSwAWT"
+HASH_WELCOME_DOCS="QmV9E5oNhFDWeRV8NQ91G7vp3pvff2S4UYkn89T5koSzqo"
 HASH_EMPTY_DIR="QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn"