Docs: Remove the blank line between @param and @return in test docblocks

[mukeshpanchal27]

Trac ticket: https://core.trac.wordpress.org/ticket/65818

Follow-up to #13063 in which it covers core file changes.

The PHP inline documentation standards place @return immediately after the last @param tag, with no blank line between them:

/**
 * Summary.
 *
 * @param string $var Description.
 * @return string Description.
 */

This corrects 65 docblocks across 29 files in the PHPUnit test suite.

Documentation-only; no functional change in tests.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5
Used for: I found a few occurrences myself, and Claude helped me identify the remaining ones and draft the PR.

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