Fix packaging step for aws-logging-dotnet

[SrutiG]

Issue #, if available:
None

Description of changes:
When running the packaging step in the aws-logging-dotnet pipeline, I encountered the following errors:

C:\Program Files\dotnet\sdk\3.1.402\Sdks\NuGet.Build.Tasks.Pack\buildCrossTargeting\NuGet.Build.Tasks.Pack.targets(198,5): error NU5125: The 'licenseUrl' element will be deprecated. Consider using the 'license' element instead. [C:\codebuild\tmp\output\src371779675\src\src\AWS.Logger.Core\AWS.Logger.Core.csproj]
--
47 | C:\Program Files\dotnet\sdk\3.1.402\Sdks\NuGet.Build.Tasks.Pack\buildCrossTargeting\NuGet.Build.Tasks.Pack.targets(198,5): error NU5048: The 'PackageIconUrl'/'iconUrl' element is deprecated. Consider using the 'PackageIcon'/'icon' element instead. Learn more at https://aka.ms/deprecateIconUrl

I encountered these errors as well when running it locally.

I fixed the PackageLicenseUrl issue by switching it to PackageLicenseExpression. Switching the PackageIconUrl to PackageIcon requires adding the image to the repository. I suppressed the error for now.

EDIT (11/9): Referenced local LICENSE file using PackageLicenseFile and added icon.png and added PackageIcon reference

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.