analyzer: Fix previously missed cases of "unintended" HTML in comments

Work towards https://github.com/dart-lang/sdk/issues/64155

The first line of these (BNF?) lines is only indented _3_ columns from the paragraph text; it must be indented 4.

Change-Id: I3761f26b5d23c9f36317f8e7b74c11713e353289
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/544461
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Auto-Submit: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>