fix: don't use `title` as video description on Facebook in social-media/PublishPost

[tmladek]

Description

input.title was used as the primary description of an uploaded Facebook video, with input.text as the fallback. This change makes it so that only input.text is considered.

Motivation and Context

This behavior is unexpected.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] I have read the CONTRIBUTING document.
• [x] I haven't repeated the code. (DRY)
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.