Remove the old x86 backend

examples/multi.rs

@@ -9,7 +9,6 @@
 
 use anyhow::Result;
 
-#[cfg(not(feature = "old-x86-backend"))]
 fn main() -> Result<()> {
     use wasmtime::*;
 
@@ -63,11 +62,3 @@ fn main() -> Result<()> {
 
     Ok(())
 }
-
-// Note that this example is not supported in the off-by-default feature of the
-// old x86 compiler backend for Cranelift. Wasmtime's default configuration
-// supports this example, however.
-#[cfg(feature = "old-x86-backend")]
-fn main() -> Result<()> {
-    Ok(())
-}