chore: add changelog entry for Batch Changes <> GitHub apps integration (#63756)

Changelog update

## Test plan

<!-- REQUIRED; info at
https://docs-legacy.sourcegraph.com/dev/background-information/testing_principles
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N/A

## Changelog

* Batch Changes: GitHub apps can now be added as a credential for
authentication and interacting with changesets.
[#31533](https://github.com/sourcegraph/sourcegraph/issues/31533)

Author: BolajiOlajide

CHANGELOG.md

@@ -31,6 +31,7 @@ All notable changes to Sourcegraph are documented in this file.
 - Added syntax highlighting for the Hack programming language. [#62770](https://github.com/sourcegraph/sourcegraph/pull/62770)
 - Batch Changes: The new (optional) field "version" of batch specs determines how the spec is processed. This allows us to introduce new features while maintaining backward compatability. [#63613](https://github.com/sourcegraph/sourcegraph/pull/63613)
 - Batch Changes: A new version `2` is introduced. Batch specs specifying `version: 2` will use keyword search as the default pattern type to determine repos/workspaces. Batch specs with `version: 1` or without version field keep using pattern type "standard". [#63613](https://github.com/sourcegraph/sourcegraph/pull/63613)
+- Batch Changes: GitHub apps can now be added as a credential for authentication and interacting with changesets. [#31533](https://github.com/sourcegraph/sourcegraph/issues/31533)
 
 ### Changed