refactor(cw): Rename the mergedTextDocument field.

[leigaol]

Problem

The mergedRelevantTextDocument should have a better name. It is actually the documents that are referenced.

Solution

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• Treat all work as PUBLIC. Private feature/x branches will not be squash-merged at release time.
• Your code changes must meet the guidelines in CONTRIBUTING.md.
• License: I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

• This pull request modifies code in src/* but no tests were added/updated.
  • Confirm whether tests should be added or ensure the PR description explains why tests are not required.