fix(comp:anchor): should default active first item

[xuemanchi]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added/updated or not needed
• Docs and demo have been added/updated or not needed

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Component style update
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Application (the showcase website) / infrastructure changes
• Other... Please describe:

What is the current behavior?

• remove default link
• use first item as reduce start, ensure default first item active works

What is the new behavior?

Other information

close #774

[idux-bot]

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