fix update-credits.sh

The script would insert an additional newline
before the Firecracker contributors.

Signed-off-by: Diana Popa <[email protected]>

Author: dianpopa

tools/update-credits.sh

@@ -28,7 +28,6 @@ written in Rust with a focus on safety and security. Thanks go to:
 * [Jason D. Clinton](https://github.com/jclinton) <[email protected]>
 * Sonny Rao <[email protected]>
 
-
 Contributors to the Firecracker repository:
 EOH
     echo