fix(#4460): drop the superfluous allow-test-rule marker

local/no-source-grep's looksLikeSourcePath only matches readFileSync
targets ending in .cjs/.cts/.js/.mjs/.mts/.ts -- WORKFLOW_PATH here
points at code-review.md, so the rule can never fire regardless of the
marker. Confirmed by reading eslint-rules/no-source-grep.cjs directly
before removing it, not assumed. Caught by an independent code-review
pass on the sibling #4466 fix, which copied this same now-unnecessary
marker pattern -- fixed there too.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/code-review-tier3-files-override-scoping.test.cjs

@@ -1,7 +1,3 @@
-// allow-test-rule: source-text-is-the-product (see #4460)
-// Workflow markdown is the installed orchestration contract — this file's
-// text IS what the reviewer flow runs at runtime.
-
 'use strict';
 
 /**