docs: update getAllPostageBatch to getPostageBatches (#1125)

* docs: update getAllPostageBatch to getPostageBatches

* test: update test coverage

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: Cafe137

README.md

@@ -200,7 +200,7 @@ The `toString` method uses `toHex`.
 | `pssSend`                            | `POST /pss/send/:topic/:target` [🔗](https://docs.ethswarm.org/api/#tag/Postal-Service-for-Swarm/paths/~1pss~1send~1%7Btopic%7D~1%7Btargets%7D/post)     | ❌✅✅   |
 | `pssSubscribe` _Websocket_           | `GET /pss/subscribe/:topic` [🔗](https://docs.ethswarm.org/api/#tag/Postal-Service-for-Swarm/paths/~1pss~1subscribe~1%7Btopic%7D/get)                    | ❌❌✅   |
 | `pssReceive`                         | `GET /pss/subscribe/:topic` [🔗](https://docs.ethswarm.org/api/#tag/Postal-Service-for-Swarm/paths/~1pss~1subscribe~1%7Btopic%7D/get)                    | ❌❌✅   |
-| `getAllPostageBatch`                 | `GET /stamps` [🔗](https://docs.ethswarm.org/api/#tag/Postage-Stamps/paths/~1stamps/get)                                                                 | ❌✅✅   |
+| `getPostageBatches`                  | `GET /stamps` [🔗](https://docs.ethswarm.org/api/#tag/Postage-Stamps/paths/~1stamps/get)                                                                 | ❌✅✅   |
 | `getGlobalPostageBatches`            | `GET /batches` [🔗](https://docs.ethswarm.org/api/#tag/Postage-Stamps/paths/~1batches/get)                                                               | ❌✅✅   |
 | `getPostageBatch`                    | `GET /stamps/:batchId` [🔗](https://docs.ethswarm.org/api/#tag/Postage-Stamps/paths/~1stamps~1%7Bbatch_id%7D/get)                                        | ❌✅✅   |
 | `getPostageBatchBuckets`             | `GET /stamps/:batchId/buckets` [🔗](https://docs.ethswarm.org/api/#tag/Postage-Stamps/paths/~1stamps~1%7Bbatch_id%7D~1buckets/get)                       | ❌✅✅   |
@@ -266,7 +266,7 @@ async function getOrCreatePostageBatch() {
   const bee = new Bee('http://localhost:1633')
   let batchId
 
-  const batches = await bee.getAllPostageBatch()
+  const batches = await bee.getPostageBatches()
   const usable = batches.find(x => x.usable)
 
   if (usable) {