[release/v7.4]Add 7.4.9 changelog (PowerShell#25171)

Co-authored-by: Justin Chung <chungjustin@microsoft.com>

Author: jshigetomi

CHANGELOG/7.4.md

@@ -1,10 +1,44 @@
 # 7.4 Changelog
 
+## [7.4.9]
+
+### Notes
+
+_This release is internal only. It is not available for download._
+
+### Tools
+
+- Check GH token availability for `Get-Changelog` (#25156)
+
+### Build and Packaging Improvements
+
+<details>
+
+<summary>
+
+<p>Update .NET SDK to 8.0.407</p>
+
+</summary>
+
+<ul>
+<li>Update branch for release (#25101)</li>
+<li>Only build Linux for packaging changes (#25161)</li>
+<li>Skip additional packages when generating component manifest (#25160)</li>
+<li>Remove Az module installs and AzureRM uninstalls in pipeline (#25157)</li>
+<li>Add GitHub Actions workflow to verify PR labels (#25158)</li>
+<li>Update security extensions (#25099)</li>
+<li>Make Component Manifest Updater use neutral target in addition to RID target (#25100)</li>
+</ul>
+
+</details>
+
+[7.4.9]: https://github.com/PowerShell/PowerShell/compare/v7.4.8...v7.4.9
+
 ## [7.4.8]
 
 ### Notes
 
-*This release is internal only.  It is not available for download.*
+_This release is internal only. It is not available for download._
 
 ### Build and Packaging Improvements