fix(PrismicRichText): prevent extra whitespace between text

[angeloashmore]

Types of changes

• Chore (a non-breaking change which is related to package maintenance)
• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

This PR fixes a bug in <PrismicRichText> where extra whitespace was added between text.

The bug was apparent when labels and plain text were used. Should the bug appear in other block types, the same whitespace-elimination strategy can be used.

Checklist:

• My change requires an update to the official documentation.
• All TSDoc comments are up-to-date and new ones have been added where necessary.
• All new and existing tests are passing.

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