Merge pull request #8845 from davidkline-ms/assetPackages251

Update release notes, fix authors formatting

Author: keveleigh

Documentation/Authors.md

@@ -45,7 +45,7 @@ The Microsoft Mixed Reality Toolkit is a collaborative project containing contri
 - JoeyBytes
 - julenka
 - julesra
- -julianloehr-kg
+- julianloehr-kg
 - jwittner
 - Kent1LG
 - keveleigh

Documentation/ReleaseNotes.md

@@ -13,9 +13,6 @@
 
 ## What's new
 
-> [!NOTE]
-> The Mixed Reality Toolkit 2.5.1 release is available exclusively via the [Unity Package Manager](usingupm.md).
-
 ### Package dependency errors fixed
 
 This release fixes incorrect inter-package file dependencies (ex: files in Standard Assets no longer incorrectly reference files in Foundation). Version 2.5.1 also adds an explicit dependency on Text Mesh Pro.