Some Flutter icon previews are missing from code completion/hover details

[DanTup]

From flutter/flutter#117384:

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Some links to icons from the Icons class are broken in the IDE tooltips.

I found that the following icons have broken links:

• Icons.arrow_outward (all variants)
• Icons.assignment_add
• Icons.assist_walker (all variants)
• Icons.barcode_reader
• Icons.battery_1 through Icons.battery_6 (all variants)
• Icons.blind (all variants)
• Icons.brightness_1 through Icons.brightness_7 (all variants)
• Icons_diversity (all variants)