Removing obsolete benchmark screenshot (#2730)

Co-authored-by: Paul Masurel <[email protected]>

Author: fulmicoton

README.md

@@ -23,8 +23,6 @@ performance for different types of queries/collections.
 
 Your mileage WILL vary depending on the nature of queries and their load.
 
-<img src="doc/assets/images/searchbenchmark.png">
-
 Details about the benchmark can be found at this [repository](https://github.com/quickwit-oss/search-benchmark-game).
 
 ## Features