Handlers and enhanced navigation 8.0

[guardrex]

Fixes #30876

Mackinnon ...

• Seems like there were two paragraphs in the content that you supplied and one was more general than the other, so I placed one a little higher than the other.
• Since these paragraphs refer to location changing handlers and that section was below the new content on enhanced nav, I moved the Location changes section above the new Enhanced navigation and form handling section.

❓Should the second paragraph end with a remark like ...

If the app must rely on a location change handler firing, don't use enhanced navigation, which is explained later in this section.

UPDATE: Yes! Let's give that line a try. You can let me know about keeping or 🔪 it on review.

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aspnetcore/blazor/fundamentals/routing.md	ASP.NET Core Blazor routing and navigation

[MackinnonBuck]

Looks good!