docs(core): remove documentation of mutate function (angular#52435)

PR Close angular#52435

Author: swami-sanapathi

aio/content/guide/signals.md

@@ -35,17 +35,6 @@ or use the `.update()` operation to compute a new value from the previous one:
 count.update(value => value + 1);
 ```
 
-When working with signals that contain objects, it's sometimes useful to mutate that object directly. For example, if the object is an array, you may want to push a new value without replacing the array entirely. To make an internal change like this, use the `.mutate` method:
-
-```ts
-const todos = signal([{title: 'Learn signals', done: false}]);
-
-todos.mutate(value => {
-  // Change the first TODO in the array to 'done: true' without replacing it.
-  value[0].done = true;
-});
-```
-
 Writable signals have the type `WritableSignal`.
 
 ### Computed signals
@@ -203,8 +192,6 @@ data.set(['test']);
 
 Equality functions can be provided to both writable and computed signals.
 
-For writable signals, `.mutate()` does not check for equality because it mutates the current value without producing a new reference.
-
 ### Reading without tracking dependencies
 
 Rarely, you may want to execute code which may read signals in a reactive function such as `computed` or `effect` _without_ creating a dependency.

packages/core/primitives/signals/README.md

@@ -16,7 +16,7 @@ This context and getter function mechanism allows for signal dependencies of a c
 
 ### Writable signals: `signal()`
 
-The `createSignal()` function produces a specific type of signal that tracks a stored value. In addition to providing a getter function, these signals can be wired up with additional APIs for changing the value of the signal (along with notifying any dependents of the change). These include the `.set` operation for replacing the signal value, `.update` for deriving a new value, and `.mutate` for performing internal mutation of the current value. In Angular, these are exposed as functions on the signal getter itself. For example:
+The `createSignal()` function produces a specific type of signal that tracks a stored value. In addition to providing a getter function, these signals can be wired up with additional APIs for changing the value of the signal (along with notifying any dependents of the change). These include the `.set` operation for replacing the signal value, and `.update` for deriving a new value. In Angular, these are exposed as functions on the signal getter itself. For example:
 
 ```typescript
 const counter = signal(0);
@@ -25,16 +25,6 @@ counter.set(2);
 counter.update(count => count + 1);
 ```
 
-The signal value can be also updated in-place, using the dedicated `.mutate` method:
-
-```typescript
-const todoList = signal<Todo[]>([]);
-
-todoList.mutate(list => {
-  list.push({title: 'One more task', completed: false});
-});
-```
-
 #### Equality
 
 The signal creation function one can, optionally, specify an equality comparator function. The comparator is used to decide whether the new supplied value is the same, or different, as compared to the current signal’s value.