Gently update docs for calibration set

[hfrick]

closes #292

Emil, would you read over this as a fresh pair of eyes to make sure it's all correct and understandable?

[Copilot]

Pull Request Overview

This PR updates documentation to improve clarity and accuracy regarding calibration data usage in postprocessor training workflows. The changes correct grammar and update function/parameter names to reflect current API conventions.

• Fixes grammatical error in postprocessor training documentation
• Updates parameter name from calibration to data_calibration for consistency
• Updates function reference from rsample::inner_split() to rsample::internal_calibration_split()

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
man/add_tailor.Rd	Updates documentation file with corrected grammar and updated parameter/function names
R/post-action-tailor.R	Updates inline documentation comments with same corrections as the .Rd file

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