Fixed image format bug + updated similarity score labels

[jackyliang]

Problem

1. Lisa reported bug on an image causing problems when uploaded.
2. Subjective similarity score labels were inaccurate

Solution

1. Replaced imghdr library with Pillow
2. Updated score labels to just use the raw score from Pinecone

Type of Change

• [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 not work as expected)
• [ ] This change requires a documentation update
• [ ] Infrastructure change (CI configs, etc)
• [ ] Non-code change (docs, etc)
• [ ] None of the above: (explain here)

Test Plan

Describe specific steps for validating this change.