fix(bcd): improve titles for support behind flags

[caugner]

Summary

Fixes #5429.

Problem

When hovering about a feature that is only supported behind a flag,

• the title of the cross icon would say "Full support", and
• the title of the flag icon would say "disabled".

Solution

1. The title on the cross icon now says "No support" to be consistent with the icon.
2. The title on the flag icon now says "User must explicitly enable this feature." like the legend.

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Screenshots

Before

After

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How did you test this change?

1. I opened http://localhost:3000/en-US/docs/Web/HTML/Element/menu#browser_compatibility locally.
2. I hovered over the icons for the feature row <hr> creates a separator and the Firefox for Android column.