Typekit fonts making paragraph text bold

Using Typekit fonts on AT Sites causes the paragraph text on the site to change weight when the font-weight of headings are changed.

**Things I've noticed:**

1. The issue is affected only on AT Sites
2. The issue is only with Typekit Fonts. Google fonts work properly
3. If different fonts are used for Headings and Paragraphs the issue doesn't appear
4. Customizer Preview looks normal, but the appearance on site is different.

**Steps to reproduce:**

1. Open any AT Site and change the font via Customizer
2. Select any Typekit font for both Headings & Paragraph and set the Heading font-size above regular.
3. Check Customizer preview to see that the changes are working as expected.
4. Open the site to see the font-weight for paragraphs are different.

**Attaching screenshots for reference:**

Customizer Preview

Original Result

Start by reproducing the issue on an AT Site with the same Typekit font selected for headings and paragraphs, then compare the Customizer preview with the live site. Confirm the behavior against Google fonts and separate heading and paragraph fonts; the fix is complete when the live paragraph weight matches the preview without regressing those comparison cases.

Written by the indexing model from the issue text.