fix(ios): large title animation now works properly in a modal

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue Number: #20696
I was using largeTitleEl instead of largeTitleBox which would result in something like undefinedpx. This didn't matter in most cases since the offset was almost always 0px, but in modals it matters.

What is the new behavior?

• Use largeTitleBox instead of largeTitleEl when determining the offsets

Does this introduce a breaking change?

• Yes
• No

Other information