fix(signals): Revert freezing from migration docs

projects/ngrx.io/content/guide/migration/v19.md

@@ -23,49 +23,6 @@ Version 19 has the minimum version requirements:
 
 ### Signals
 
-#### Throw error in dev mode on state mutation
-
-The `patchState` method applies a deep freeze on the state in dev mode.
-If you try to update the state directly, it will throw an error in dev mode.
-
-BEFORE:
-
-```ts
-const userState = signalState(initialState);
-patchState(userState, (state) => {
-  // mutable change which went through
-  state.user.firstName = 'mutable change';
-  return state;
-});
-```
-
-AFTER:
-
-```ts
-const userState = signalState(initialState);
-patchState(userState, (state) => {
-  // mutable change throws in dev mode
-  state.user.firstName = 'mutable change'; 
-  return state;
-});
-```
-
-To fix the error, update the state in an immutable way.
-
-```ts
-const userState = signalState(initialState);
-patchState(userState, (state) => {
-  return {
-    ...state,
-    user: {
-      ...state.user,
-      // immutable change which went through
-      firstName: 'immutable change', 
-    },
-  };
-});
-```
-
 #### `computed` is replaced with `props`
 
 To support more cases, the `props` property is added to  `signalStoreFeature`, which replaces the existing `computed` property.