fix(textarea): update innerHTML to value

[pixelflips]

Description

The textarea's value is not being set properly in the textarea component. This value is currently updated by innerHTML when onTextareaChange is triggered.

Instead of innerHTML, we should use the recommended textarea.value to ensure the content matches what the user types.

Fixes https://kajabi.atlassian.net/browse/DSS-1165

🎩 :hattip to @ju-Skinner for the assist here.

Type of change

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• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• unit tests
• e2e tests
• accessibility tests
• tested manually
• other:

Test Configuration:

• Pine versions:
• OS:
• Browsers:
• Screen readers:
• Misc:

Checklist:

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• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes
• Design has QA'ed and approved this PR

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[monicawheeler]

Non-blocker: did we want to update the documentation alongside this change, as mentioned in the team sync?

[ju-Skinner]

@monicawheeler I don't believe that we need to. The reason is that we expose the property value and are using value from the underlying textarea so it's a 1:1 match now.

I'm open for further team discussion though.

[monicawheeler]

@ju-Skinner makes sense! Carry on!