docs: Fix config schema

It seems like jsonschema2md ironically doesn't validate the schema of the input
it receives. :)

It fails horribly with:

```
file:///home/cklein/elastisys/welkin/node_modules/@adobe/jsonschema2md/lib/markdownBuilder.js:697
        ...schema[keyword`examples`].map((example) => paragraph(code('yaml', yaml.dump(example, undefined, 2)))),
                                     ^

TypeError: schema[keyword].map is not a function or its return value is not iterable
    at makeexamples (file:///home/cklein/elastisys/welkin/node_modules/@adobe/jsonschema2md/lib/markdownBuilder.js:697:38)
    at file:///home/cklein/elastisys/welkin/node_modules/@adobe/jsonschema2md/lib/markdownBuilder.js:762:14
    at Array.map (<anonymous>)
    at makeproplist (file:///home/cklein/elastisys/welkin/node_modules/@adobe/jsonschema2md/lib/markdownBuilder.js:750:54)
    at file:///home/cklein/elastisys/welkin/node_modules/@adobe/jsonschema2md/lib/markdownBuilder.js:831:16
    at Array.map (<anonymous>)
    at makedefinitions (file:///home/cklein/elastisys/welkin/node_modules/@adobe/jsonschema2md/lib/markdownBuilder.js:818:10)
    at file:///home/cklein/elastisys/welkin/node_modules/@adobe/jsonschema2md/lib/markdownBuilder.js:888:10
    at /home/cklein/elastisys/welkin/node_modules/ferrum/src/sequence.js:1234:12
    at /home/cklein/elastisys/welkin/node_modules/ferrum/src/sequence.js:807:5
```

I added `console.log(schema[keyword`examples`]);` before the failing line and,
long story short, it seems like jsonschema2md expects a list of examples and not
a string.

Author: cristiklein

config/schemas/config.yaml

@@ -4283,7 +4283,8 @@ properties:
             description: Configure a pattern of node groups to exclude from the resource request alerts. This can be used to exclude certain node groups from request alerts, while still getting usage alerts for those node groups.
             type: string
             default: ""
-            examples: ".*redis.*|.*postgres.*"
+            examples:
+              - ".*redis.*|.*postgres.*"
       diskAlerts:
         title: Disk Alerts
         description: Definitions for disk alerts.