Update local state docs

* Use the term mutation more to help developers search for what they
  want
* Wordsmith existing section to emphasize that local-only mutations
  aren't really "a thing" anymore - use reactive variables or writeQuery
  / writeFragment instead

docs/source/local-state/managing-state-with-field-policies.mdx

@@ -99,16 +99,16 @@ That's it! The `@client` directive tells Apollo Client that `isInCart` is a loca
 >
 > </ExpansionPanel>
 
-## Storing
+## Storing and mutations
 
-You can use Apollo Client to query local state, regardless of how you _store_ that state. Apollo Client provides a couple of optional but helpful mechanisms for representing local state:
+You can use Apollo Client to query and modify local state, regardless of how you _store_ that state. Apollo Client provides a couple of optional but helpful mechanisms for representing local state:
 
 * [Reactive variables](#storing-local-state-in-reactive-variables)
 * [The Apollo Client cache itself](#storing-local-state-in-the-cache)
 
-> **Note:** Apollo Client >= 3 no longer recommends the [local resolver](./local-resolvers) approach of using `client.mutate` / `useMutation` combined with an `@client` mutation operation to [update local state](./local-resolvers/#local-resolvers). To update local state, we recommend using [`writeQuery`](../caching/cache-interaction/#writequery), [`writeFragment`](../caching/cache-interaction/#writefragment), or [reactive variables](./reactive-variables/).
+It's tempting to think of local-only mutations as being expressed similarly to other local-only fields. When using previous versions of Apollo Client, developers would define local-only mutations using `@client`. They would then use [local resolvers](./local-resolvers) to handle `client.mutate` / `useMutation` calls. This is no longer the case, however. For Apollo Client version >= 3 users we recommend using [`writeQuery`](../caching/cache-interaction/#writequery), [`writeFragment`](../caching/cache-interaction/#writefragment), or [reactive variables](./reactive-variables/) to manage local state.
 
-### Storing local state in reactive variables
+### Storing and updating local state with reactive variables
 
 Apollo Client [reactive variables](./reactive-variables) are great for representing local state:
 
@@ -238,7 +238,7 @@ As with the preceding `useQuery` example, whenever the `cartItemsVar` variable i
 
 > **Important:** If you call `cartItemsVar()` instead of `useReactiveVar(cartItemsVar)` in the example above, future variable updates _do not_ cause the `Cart` component to rerender.
 
-### Storing local state in the cache
+### Storing and modifying local state in the cache
 
 Storing local state directly in the Apollo Client cache provides some advantages, but usually requires more code than [using reactive variables](#storing-local-state-in-reactive-variables):