Update RegionInfo.xml (#4560)

RegionInfo.Name is behaving differently in .NET Framework than .NET Core. This PR is to clarify that in the docs.

Author: tarekgh

xml/System.Globalization/RegionInfo.xml

@@ -1110,7 +1110,7 @@
 ## Remarks  
  If the current <xref:System.Globalization.RegionInfo> object is created with the <xref:System.Globalization.RegionInfo.%23ctor%28System.Int32%29?displayProperty=nameWithType> constructor that takes a culture identifier parameter, the <xref:System.Globalization.RegionInfo.Name%2A> property value is one of the two-letter codes defined in ISO 3166 for the country/region and is formatted in uppercase. For example, the two-letter code for the United States is "US".  
   
- If the current <xref:System.Globalization.RegionInfo> object is created with the <xref:System.Globalization.RegionInfo.%23ctor%28System.String%29?displayProperty=nameWithType> constructor and is passed a full culture name such as "en-US", the <xref:System.Globalization.RegionInfo.Name%2A> property value is a full culture name and not just the region name.  
+ If the current <xref:System.Globalization.RegionInfo> object is created with the <xref:System.Globalization.RegionInfo.%23ctor%28System.String%29?displayProperty=nameWithType> constructor and is passed a full culture name such as "en-US", the <xref:System.Globalization.RegionInfo.Name%2A> property value is a full culture name in .NET Framework and just the region name in .NET Core.