Update consecutive dots remarks

[gewarren]

Fixes dotnet/docs#50592.

Also does other cleanup in the file. (So hide whitespace changes.)

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/ncl

[Copilot]

Pull request overview

This PR updates the documentation for the MailAddress class to clarify that consecutive dots in user names are only allowed in .NET 9 and earlier, and are no longer permitted starting in .NET 10. The changes also include general formatting improvements and modernization of the documentation style.

• Moves the consecutive dots remark from the allowed elements section to both the allowed and unsupported sections with version-specific notes
• Updates property references from older %2A format to cleaner inline link format
• Removes redundant "## Remarks" and "## Examples" headers, improves whitespace and formatting consistency

[ManickaP]

Thanks.