Disable an incorrect optimization in int64ToString

packages/runtime/spec/pb-long.spec.ts

@@ -1,4 +1,5 @@
 import {PbLong, PbULong} from "../src";
+import {int64toString} from '../src/goog-varint';
 
 
 describe('PbULong', function () {
@@ -72,6 +73,14 @@ describe('PbULong', function () {
         expect(ulong.lo).toBe(0);
     });
 
+    it('int64toString should serialize the same was as BigInt.toString()', function () {
+        let ulong = PbULong.from(1661324400000);
+        expect(ulong.hi).toBe(386);
+        expect(ulong.lo).toBe(-827943552);
+        expect(ulong.toString()).toBe('1661324400000')
+        expect(int64toString(ulong.lo, ulong.hi)).toBe('1661324400000')
+    });
+
 });
 
 
@@ -302,4 +311,3 @@ describe('testing native bigint', function () {
     });
 
 });
-

packages/runtime/src/goog-varint.ts

@@ -175,12 +175,6 @@ export function int64fromString(dec: string): [boolean, number, number] {
  * Copyright 2008 Google Inc.
  */
 export function int64toString(bitsLow: number, bitsHigh: number): string {
-    // Skip the expensive conversion if the number is small enough to use the
-    // built-in conversions.
-    if (bitsHigh <= 0x1FFFFF) {
-        return '' + (TWO_PWR_32_DBL * bitsHigh + bitsLow);
-    }
-
     // What this code is doing is essentially converting the input number from
     // base-2 to base-1e7, which allows us to represent the 64-bit range with
     // only 3 (very large) digits. Those digits are then trivial to convert to