Fix TypeScript Compiler Errors in Vertex Tests #12945

Job	Run time
Build Firestore	8m 32s
Test Firestore Compatible on Firefox	5m 48s
Test Firestore (test:browser)	9m 44s
Test Firestore (test:travis)	3m 47s
Test Firestore Compatible	5m 21s
Test Firestore on Firefox (test:browser)	8m 51s
Test Firestore (test:lite:browser)	1m 27s
Test Nightly Firestore with Chrome	0s
Test Firestore on Firefox (test:travis)	4m 11s
Test Firestore (test:browser:prod:nameddb)	9m 5s
Test Firestore on Firefox (test:lite:browser)	1m 47s
Test Firestore (test:lite:browser:nameddb)	1m 39s
Test Firestore on Webkit (test:browser)	12m 16s
Test Firestore on Firefox (test:browser:prod:nameddb)	8m 23s
Test Firestore Compatible on Webkit	5m 55s
Test Firestore on Webkit (test:lite:browser)	2m 1s
Test Firestore on Firefox (test:lite:browser:nameddb)	2m 0s
Test Firestore on Webkit (test:browser:prod:nameddb)	10m 9s
Test Firestore on Webkit (test:lite:browser:nameddb)	2m 38s
Check all required tests results	1s
	1h 43m 35s

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