fix: Add example of array attribute to telemetry attributes (#15994)

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Original:
https://develop.sentry.dev/sdk/telemetry/attributes/
Vercel preview:


## DESCRIBE YOUR PR
Adds an example of the `array` type attribute, to avoid confusion about
needing to send `integer[]` as the type.

Defined in Relay:
https://github.com/getsentry/relay/blob/master/relay-event-schema/src/protocol/attributes.rs#L158
(added in getsentry/relay#5394 with [examples
here](https://github.com/getsentry/relay/pull/5394/changes#diff-59db6f882cc2165a2f15dccf0fb5600c27bccbd508620327834b62f6dd1499a4R683))

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## PRE-MERGE CHECKLIST

*Make sure you've checked the following before merging your changes:*

- [ ] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter
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Author: JoshuaMoelans

develop-docs/sdk/telemetry/attributes.mdx

@@ -19,10 +19,18 @@ Attributes are stored as key-value pairs where each value is an object with type
     "value": 123,
     "unit": "millisecond",
     "type": "integer"
-  }
+  },
+  "my_list": {
+    "value": [1, 2, 3],
+    "type": "array"
+  },
 }
 ```
 
+<Alert>
+Sentry only supports <strong>non-mixed arrays</strong> as attribute values (e.g., all elements must be of the same type). Attributes with the 'array' type are not yet visible in the Sentry UI.
+</Alert>
+
 ### Properties
 
 | Property | Type | Required | Description |
@@ -86,4 +94,3 @@ The following units are [supported by Relay](https://getsentry.github.io/relay/r
 ## Semantic Conventions
 
 See [Sentry Conventions](https://github.com/getsentry/sentry-conventions/) for a full list of supported attributes.
-