Remove spec interpreter fuzz target temporarily (#3399)

This commit removes the `differential_spec` fuzz target for now,
although this removal is intended to be temporary. We have #3251 to
track re-enabling the spec interpreter in a way that it won't time out,
and additionally the spec interpreter is also failing to build with
ocaml on oss-fuzz so that will also need to be investigated when
re-enabling.

fuzz/Cargo.toml

@@ -52,12 +52,6 @@ path = "fuzz_targets/differential.rs"
 test = false
 doc = false
 
-[[bin]]
-name = "differential_spec"
-path = "fuzz_targets/differential_spec.rs"
-test = false
-doc = false
-
 [[bin]]
 name = "differential_wasmi"
 path = "fuzz_targets/differential_wasmi.rs"

fuzz/fuzz_targets/differential_spec.rs

@@ -1,31 +0,0 @@
-#![no_main]
-
-use libfuzzer_sys::fuzz_target;
-use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
-use wasmtime_fuzzing::{generators, oracles};
-
-// Keep track of how many WebAssembly modules we actually executed (i.e. ran to
-// completion) versus how many were tried.
-static TRIED: AtomicUsize = AtomicUsize::new(0);
-static EXECUTED: AtomicUsize = AtomicUsize::new(0);
-
-fuzz_target!(|data: (
-    generators::Config,
-    wasm_smith::ConfiguredModule<oracles::SingleFunctionModuleConfig<false, false>>
-)| {
-    let (config, mut wasm) = data;
-    wasm.module.ensure_termination(1000);
-    let tried = TRIED.fetch_add(1, SeqCst);
-    let executed = match oracles::differential_spec_execution(&wasm.module.to_bytes(), &config) {
-        Some(_) => EXECUTED.fetch_add(1, SeqCst),
-        None => EXECUTED.load(SeqCst),
-    };
-    if tried > 0 && tried % 1000 == 0 {
-        println!(
-            "=== Execution rate ({} executed modules / {} tried modules): {}% ===",
-            executed,
-            tried,
-            executed as f64 / tried as f64 * 100f64
-        )
-    }
-});