update README

- remove expired bug bounty
- add CMake dependency

README.md

@@ -5,13 +5,6 @@
 
 ---
 
-**NEW: Cannon is currently the object of [a bug bounty on Immunefi](https://immunefi.com/bounty/optimismcannon/). Find vulnerabilities
-in Cannon for up to a $50.000 payout.**
-
-- Please take note of [the honest defender assumption](https://github.com/ethereum-optimism/cannon/issues/63)
-
----
-
 The cannon (cannon cannon cannon) is an on chain interactive dispute engine implementing EVM-equivalent fault proofs.
 
 It's half geth, half MIPS, and whole awesome.
@@ -37,7 +30,7 @@ contracts -- A Merkleized MIPS processor on chain + the challenge logic
 
 ## Building
 
-Pre-requisites: Go, Node.js, and Make.
+Pre-requisites: Go, Node.js, Make, and CMake.
 
 ```
 make build