Added Microsoft.Azure.Attestation.dll to RequiredAssemblies in Az.Attestation.psd1 file

Author: gkostal

src/Attestation/Attestation/Az.Attestation.psd1

@@ -56,7 +56,7 @@ DotNetFrameworkVersion = '4.7.2'
 RequiredModules = @(@{ModuleName = 'Az.Accounts'; ModuleVersion = '1.7.1'; })
 
 # Assemblies that must be loaded prior to importing this module
-RequiredAssemblies = 'Microsoft.Azure.Management.Attestation.dll'
+RequiredAssemblies = 'Microsoft.Azure.Management.Attestation.dll','Microsoft.Azure.Attestation.dll'
 
 # Script files (.ps1) that are run in the caller's environment prior to importing this module.
 # ScriptsToProcess = @()