Update changelog for 4.27.0 release (#2422)
Update changelog for 4.27.0 release (#2422)

* Update changelog for 4.27.0 release

* Update changelog.txt

* Update changelog.txt

Co-authored-by: jennyf19 <5916738f30947fed0b076ca8e936e9b1c1f5e5b5@microsoft.com>

Co-authored-by: jennyf19 <5916738f30947fed0b076ca8e936e9b1c1f5e5b5@microsoft.com>
AzureAD/microsoft-authentication-library-for-dotnet,AzureAD/microsoft-authentication-library-for-dotnet,AzureAD/microsoft-authentication-library-for-dotnet,AzureAD/microsoft-authentication-library-for-dotnet