Fixed copyright element (#7087)

Summary of the changes:
 - Updated copyright symbol
 - Changed file encoding to UTF-8 without BOM

Fixes #7065

src/Components/Blazor/Cli/src/Microsoft.AspNetCore.Blazor.Cli.nuspec

-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <package xmlns="http://schemas.microsoft.com/packaging/2013/05/nuspec.xsd">
   <metadata>
     <id>Microsoft.AspNetCore.Blazor.Cli</id>
@@ -12,7 +12,7 @@
     <description>Development server for use when building Blazor applications.
 
 This package was built from the source code at https://github.com/aspnet/AspNetCore/tree/$repositorycommit$</description>
-    <copyright> Microsoft Corporation. All rights reserved.</copyright>
+    <copyright>© Microsoft Corporation. All rights reserved.</copyright>
     <tags>aspnetcore components</tags>
     <serviceable>true</serviceable>
     <repository type="git" url="https://github.com/aspnet/AspNetCore" commit="$repositorycommit$" />