Remove outdated lint

[olivereanderson]

Description of change

This removes the lintPtrNullWithoutFree(content) function which is used when building the Wasm/TS/JS bindings.

The lint was introduced to catch generated code that nulls out Wasm pointers without de-registering the finalizer (we build our bindings with the --weak-refs flag for automatic garbage collection see this section of the wasm-bindgen reference).

As of wasm-bindgen PR #3117 which is included in version 0.2.84 of wasm-bindgen such problematic code is no longer generated hence the lint is no longer needed.

How the change has been tested

Tested building this code (in wasm_core_did.rs)

impl WasmCoreDID {
  //.. 

  /// Swaps the contents and consumes `other`.  
  #[wasm_bindgen]
  pub fn swap(&mut self, mut other: WasmCoreDID) {
    std::mem::swap(&mut self.0, &mut other.0);
  }
  
  #[wasm_bindgen(js_name = moveOther)]
  pub fn move_other(other: WasmCoreDID) -> WasmCoreDID {
    other
    }
 }

#[wasm_bindgen]
extern "C" {
  #[wasm_bindgen(typescript_type = "CoreDID | ICoreDID")]
  pub type ICoreDID;

  #[wasm_bindgen(method, js_name= toCoreDid)]
  pub fn to_core_did(this: &ICoreDID) -> WasmCoreDID;

}

with wasm-bindgen version 0.2.83 and 0.2.84. In the former the lint is triggered by all three of those functions, while in version 0.2.84 the lint passes.

Change checklist

Add an x to the boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes