validation: Bump rc in sepolia standard-releases (#796)

Author: sebastianst

validation/standard/standard-versions-sepolia.toml

@@ -5,8 +5,8 @@
 #   * proxied             : specify a standard "implementation_address"
 #   * neither             : specify neither a standard "address" nor "implementation_address"
 
-# Holocene https://github.com/ethereum-optimism/optimism/releases/tag/op-contracts%2Fv1.8.0-rc.3
-[releases."op-contracts/v1.8.0-rc.3"]
+# Holocene https://github.com/ethereum-optimism/optimism/releases/tag/op-contracts%2Fv1.8.0-rc.4
+[releases."op-contracts/v1.8.0-rc.4"]
 # Updated in this release
 system_config = { version = "2.3.0", implementation_address = "0x33b83E4C305c908B2Fc181dDa36e230213058d7d" } # UPDATED IN THIS RELEASE
 fault_dispute_game = { version = "1.3.1" }                                                                   # UPDATED IN THIS RELEASE