refactor: remove redundant checks in legacy debt verification

- Removed redundant `isPreExisting` and metadata existence checks from `verifyIsPreExisting` in `scripts/create-review-issues.ts`, as these are already enforced by the caller's filtering and the Zod schema validation.
- Verified that all unit tests in `scripts/__tests__` and `tests/unit/scripts` continue to pass successfully.
- Confirmed that linting and build checks pass without errors.
- Maintained strict 50-character minimum for descriptions and required metadata for verifiable debt.

Co-authored-by: arii <342438+arii@users.noreply.github.com>

Author: google-labs-jules[bot]

scripts/create-review-issues.ts

@@ -479,10 +479,6 @@ function verifyIsPreExisting(
   issue: SuggestedIssue,
   baseSha: string | undefined
 ): boolean {
-  if (!issue.isPreExisting) return false
-  // Requirements are now enforced by Zod schema, but keeping check for type safety
-  if (!issue.filePath || !issue.lineNumber) return false
-
   try {
     const range = `${issue.lineNumber},${issue.lineNumber}`
     // Use git blame to see if the line was modified since baseSha