Remove wrong suggestion part (#983)

Author: HKalbasi

blog/content/edition-2/posts/11-allocator-designs/index.md

@@ -172,9 +172,6 @@ Note that we don't perform any bounds checks or alignment adjustments, so this i
 error[E0594]: cannot assign to `self.next` which is behind a `&` reference
   --> src/allocator/bump.rs:29:9
    |
-26 |     unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
-   |                     ----- help: consider changing this to be a mutable reference: `&mut self`
-...
 29 |         self.next = alloc_start + layout.size();
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be written
 ```
@@ -186,8 +183,6 @@ The error occurs because the [`alloc`] and [`dealloc`] methods of the `GlobalAll
 [`alloc`]: https://doc.rust-lang.org/alloc/alloc/trait.GlobalAlloc.html#tymethod.alloc
 [`dealloc`]: https://doc.rust-lang.org/alloc/alloc/trait.GlobalAlloc.html#tymethod.dealloc
 
-Note that the compiler suggestion to change `&self` to `&mut self` in the method declaration does not work here. The reason is that the method signature is defined by the `GlobalAlloc` trait and can't be changed on the implementation side. (I opened an [issue](https://github.com/rust-lang/rust/issues/68049) in the Rust repository about the invalid suggestion.)
-
 #### `GlobalAlloc` and Mutability
 
 Before we look at a possible solution to this mutability problem, let's try to understand why the `GlobalAlloc` trait methods are defined with `&self` arguments: As we saw [in the previous post][global-allocator], the global heap allocator is defined by adding the `#[global_allocator]` attribute to a `static` that implements the `GlobalAlloc` trait. Static variables are immutable in Rust, so there is no way to call a method that takes `&mut self` on the static allocator. For this reason, all the methods of `GlobalAlloc` only take an immutable `&self` reference.