Cleanup normalizeGroupCallTimestamp non-number handling

ts/util/ringrtc/normalizeGroupCallTimestamp.ts

@@ -2,31 +2,12 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /**
- * Normalizes group call timestamps (`addedTime` and `speakerTime`) into numbers. We
- * expect RingRTC to send a string, but it sends a malformed number as of this writing,
- * RingRTC 2.8.3.
- *
- * We could probably safely do `Number(fromRingRtc)` and be done, but this is extra-
- * careful.
+ * Normalizes RingRTC group call timestamps (`addedTime` and `speakerTime`) into numbers.
  */
 export function normalizeGroupCallTimestamp(
-  fromRingRtc: unknown
+  fromRingRtc: string
 ): undefined | number {
-  let asNumber: number;
-
-  switch (typeof fromRingRtc) {
-    case 'number':
-      asNumber = fromRingRtc;
-      break;
-    case 'string':
-      asNumber = parseInt(fromRingRtc.slice(0, 15), 10);
-      break;
-    case 'bigint':
-      asNumber = Number(fromRingRtc);
-      break;
-    default:
-      return undefined;
-  }
+  const asNumber = parseInt(fromRingRtc.slice(0, 15), 10);
 
   if (Number.isNaN(asNumber) || asNumber <= 0) {
     return undefined;