FIX: Align FrostedGlassPromo values with Image component props

[alex-magana]

Resolves JIRA [number]

Overall changes

A very high-level summary of easily-reproducible changes that can be understood by non-devs, and why these changes where made.

Code changes

• Use srcSet instead of srcset to match the Image component props, to ensure the srcset attribute is included in the rendered img element.

Testing

1. Visit http://localhost:7080/russian/news-55041160
2. Inspect the promos in the Feature Analysis section.
3. The promos should include the srcset attribute in the img element.

Before

After

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