fix: do not add Twitter card meta tag if image is missing

[lex111]

Pre-flight checklist

• [x] I have read the Contributing Guidelines on pull requests.
• [x] If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• [x] If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

Maybe I am misunderstanding again, but it seems we don't need to add twitter:card meta tag if there is no image for social media on web page.

Test Plan

Test links

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Related issues/PRs

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[slorber]

User can provide a social card without using the <PageMetadata> component so I'd prefer not remove the defaults