PVF: Remove artifact persistence across restarts (#2895)

Considering the complexity of
https://github.com/paritytech/polkadot-sdk/pull/2871 and the discussion
therein, as well as the further complexity introduced by the hardening
in https://github.com/paritytech/polkadot-sdk/pull/2742, as well as the
eventual replacement of wasmtime by PolkaVM, it seems best to remove
this persistence as it is creating more problems than it solves.

## Related

Closes https://github.com/paritytech/polkadot-sdk/issues/2863

polkadot/node/core/pvf/common/src/lib.rs

@@ -31,8 +31,6 @@ pub use sp_tracing;
 
 const LOG_TARGET: &str = "parachain::pvf-common";
 
-pub const RUNTIME_VERSION: &str = env!("SUBSTRATE_WASMTIME_VERSION");
-
 use parity_scale_codec::{Decode, Encode};
 use std::{
 	io::{self, Read, Write},