Update H1s to avoid duplication with vblang repo

[Youssef1313]

The dotnet/docs repository is built from both csharplang and vblang repositories.

Currently, duplicate-h1s is a suggestion that will become a warning next month.

This PR adds suffix to the headings to avoid duplication with vblang repo.

I'll open a PR in vblang to maintain consistency.

Related to dotnet/docs#19929

[Youssef1313]

@333fred Thanks for review. I've applied your suggestion. I'll also do the same in the PR for vblang now

[BillWagner]

@Youssef1313 This may not be necessary. I've started an internal dialog about the duplicate headers suggestion.

There are a couple reasons I'd prefer an engineering solution for publishing these on docs:

• We won't be adding the extra text for the ECMA standard. Adding it to the source means we need to strip it off before submitting to ECMA or ISO. That means more work on the tool that converts markdown to Word for the standard orgs.
• There's also F#, which is hosted in a different location. That language spec has similar duplicated titles.
• The reason for the suggestion is SEO, and there are other clues for better SEO success: the URL, the title suffix for example.

Let's not close this, but let's wait before merging or spending more time improving them.