fix(Tearsheet): Tearsheet scroll issue with dynamic elements

[jlongshore]

Closes #8031

Dynamically added components causing multiple scrollbars

What did you change?

• Modified Tearsheet scss
• Updated snapshots

How did you test and verify your work?

• Running tests
• Visual checks in Storybook
• Added modified code to Stackblitz supplied by bug reporter - but unsure if the dynamic nature of the example is a true representation of the application or just an example that displayed the scrollbars...

PR Checklist

As the author of this PR, before marking ready for review, confirm you:

• Reviewed every line of the diff
• Updated documentation and storybook examples
• Wrote passing tests that cover this change
• Addressed any impact on accessibility (a11y)
• Tested for cross-browser consistency
• Validated that this code is ready for review and status checks should pass

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.91%. Comparing base (f991fc1) to head (1256308).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8227   +/-   ##
=======================================
  Coverage   83.91%   83.91%           
=======================================
  Files         394      394           
  Lines       17944    17944           
  Branches     4165     4165           
=======================================
  Hits        15057    15057           
  Misses       2887     2887           

Components	Coverage Δ
ibm-products	81.98% <ø> (ø)
ibm-products-web-components	86.72% <ø> (ø)

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