Add missing `render_gfm` import to files

Several files are missing render_gfm imports resulting in failing several tests when being run separately^

• spec/javascripts/notes/components/note_body_spec.js
• spec/javascripts/vue_shared/components/markdown/field_spec.js
• spec/javascripts/blob/viewer/index_spec.js

See #67206 (moved) for details

Does this MR meet the acceptance criteria?

Conformity

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• [-] Documentation created/updated or follow-up review issue created
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