docs/guides/guide-vmcluster-multiple-retention-setup: fix some typos (#8112)

### Describe Your Changes

- fix typo in text
- fix typos in schema, re-create schema and upload source

Current doc:
https://docs.victoriametrics.com/guides/guide-vmcluster-multiple-retention-setup/

Here is an updated schema preview:

![image](https://github.com/user-attachments/assets/a65613c0-f3f6-4df5-bc70-fd70f1677386)

### Checklist

The following checks are **mandatory**:

- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).

Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
(cherry picked from commit 8772288bd6)

docs/guides/guide-vmcluster-multiple-retention-setup/README.md

@@ -28,7 +28,7 @@ The diagram below shows a proposed solution
 
 1. Groups of vminserts A know about only vmstorages A and this is explicitly specified via `-storageNode` [configuration](https://docs.victoriametrics.com/cluster-victoriametrics/#cluster-setup). 
 1. Groups of vminserts B know about only vmstorages B and this is explicitly specified via `-storageNode` [configuration](https://docs.victoriametrics.com/cluster-victoriametrics/#cluster-setup). 
-1. Groups of vminserts C know about only vmstorages A and this is explicitly specified via `-storageNode` [configuration](https://docs.victoriametrics.com/cluster-victoriametrics/#cluster-setup). 
+1. Groups of vminserts C know about only vmstorages C and this is explicitly specified via `-storageNode` [configuration](https://docs.victoriametrics.com/cluster-victoriametrics/#cluster-setup). 
 1. vmselect reads data from all vmstorage nodes via `-storageNode` [configuration](https://docs.victoriametrics.com/cluster-victoriametrics/#cluster-setup) 
    with [deduplication](https://docs.victoriametrics.com/cluster-victoriametrics/#deduplication) setting equal to vmagent's scrape interval or minimum interval between collected samples. 
 1. vmagent routes incoming metrics to the given set of `vminsert` nodes using relabeling rules specified at `-remoteWrite.urlRelabelConfig` [configuration](https://docs.victoriametrics.com/vmagent/#relabeling).