[search-documents] package fail to build with TypeScript 5.4

[jeremymeng]

1. upgrade typescript to ~5.4.5
2. rush build -t search-documents

Actual:

test/narrowedTypes.ts(59,9): error TS2322: Type 'string' is not assignable to type 'never'.
test/narrowedTypes.ts(213,9): error TS2322: Type 'string' is not assignable to type 'never'.
test/narrowedTypes.ts(254,11): error TS2322: Type 'string' is not assignable to type 'never'.

Expected:
package builds fine.