Revert "Temporarily disable SIMD fuzzing on CI" (#3555)

This reverts commit 95e8723d0767556f0ddbc9151bce269464852bb1.

crates/fuzzing/src/generators.rs

@@ -213,6 +213,12 @@ impl wasm_smith::Config for WasmtimeDefaultConfig {
         4
     }
 
+    // Turn some wasm features default-on for those that have a finished
+    // implementation in Wasmtime.
+    fn simd_enabled(&self) -> bool {
+        true
+    }
+
     fn reference_types_enabled(&self) -> bool {
         true
     }

crates/fuzzing/src/lib.rs

@@ -40,6 +40,7 @@ pub fn fuzz_default_config(strategy: wasmtime::Strategy) -> anyhow::Result<wasmt
         .wasm_reference_types(true)
         .wasm_module_linking(true)
         .wasm_multi_memory(true)
+        .wasm_simd(true)
         .wasm_memory64(true)
         .strategy(strategy)?;
     Ok(config)