Fix the NLog guide's option names and set-tag example #5716

Two errors in the NLog docs that predate 7.0.0:

• The options list in docs/platforms/dotnet/guides/nlog/index.mdx documents SendEventPropertiesAsData and SendEventPropertiesAsTags. Neither exists on SentryNLogOptions or SentryTarget. The real option is IncludeEventPropertiesAsTags. Check the rest of the list against src/Sentry.NLog/SentryNLogOptions.cs and SentryTarget.cs while you're there.
• The C# and F# tabs of platform-includes/enriching-events/set-tag/dotnet.nlog.mdx call scope.SetTag("logger", "${logger}"), with the comment "You can still use NLog layouts in code to set configured properties". The Sentry scope doesn't render NLog layouts, so the tag value is the literal string ${logger}. Only tags configured on the target (in NLog.config or through SentryNLogOptions) are rendered as layouts.

Both fixes are accurate for 6.x, so they can merge now.

getsentry/sentry-docs#19925 (merges at 7.0.0 GA) also edits both files: it removes InitializeSdk from the options list and dsn from the set-tag target. Expect a small conflict there when it merges master.