[clang-tools-extra] [clang-doc] Replace HTML-CHECK commands with HTML-CHECK-NEXT commands (PR #181330)

[Samrudh Nelli via cfe-commits]

SamrudhNelli wrote:

@ilovepi Thank you for your detailed feedbacks. 
Removed those brittle navbar checks and the checks for scripts and styles (need your insight on this). 
Removed the regex checks and used CHECK: in the next line.
Tried to enforce the style of CHECK: for major a div/section and CHECK-NEXT for commands inside it. 
Used CHECK-LABEL: for main, head, body, html.

Need your insight on whether to check all the divs present or just the important inner divs. Currently checks all the divs.

https://github.com/llvm/llvm-project/pull/181330