fix(generator filter): Replace assignment with comparator

[abcdam]

Fixed typo in filter component produced by vector generate

Summary

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Untested. I stumbled upon it while playing around with vector generate in the cli.
Can be reproduced with e.g. # vector generate /filter. If this PR doesn't follow the guidelines, feel free to delete it and push the fix.

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Please read our Vector contributor resources.
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
  run dd-rust-license-tool write to regenerate the license inventory and commit the changes (if any). More details here.

References

[bits-bot]

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