Fix code snippet attributes for baby fuzzer

Specifically:
- Remove unnecessary `compile_fail` attribute
- Add `ignore` attribute to the snippets of the complete baby fuzzer. As
  explained in [AFLplusplus#1290], it is expected for the baby fuzzer to return a
  non-0 exit code, so this should not trigger a failure during `mdbook
  test`.

docs/src/baby_fuzzer/baby_fuzzer.md

@@ -143,7 +143,7 @@ Now we want to turn our simple fuzzer into a feedback-based one and increase the
 We represent such map as a `static mut` variable.
 As we don't rely on any instrumentation engine, we have to manually track the satisfied conditions by `signals_set` in our harness:
 
-```rust,compile_fail
+```rust
 {{#rustdoc_include ../../listings/baby_fuzzer/listing-05/src/main.rs:signals}}
 ```
 
@@ -188,15 +188,15 @@ For instance, the `MutationalStage` executes the harness several times in a row,
 
 As the last step, we create a MutationalStage that uses a mutator inspired by the havoc mutator of AFL.
 
-```rust
+```rust,ignore
 {{#rustdoc_include ../../listings/baby_fuzzer/listing-06/src/main.rs:mutational_stage}}
 ```
 
 `fuzz_loop` will request a testcase for each iteration to the fuzzer using the scheduler and then it will invoke the stage.
 
 Again, we need to add the new `use` directives:
 
-```rust
+```rust,ignore
 {{#rustdoc_include ../../listings/baby_fuzzer/listing-06/src/main.rs:use}}
 ```