Conditional thresholds produce weird behaviour with Infinity value

**Describe the bug**
With the discribe plugin, the relativeTime plugin and the updateLocale plugin, I'm parsing an ISO 8601 string.
If I want to add Infinity as limiter for thresholds inside the relativeTime plugin with a ternary operation, for each Time Units, it will produce weird behaviours.

To Reproduce
```JS
import dayjs from "dayjs";
import duration from "dayjs/plugin/duration";
import relativeTime from "dayjs/plugin/relativeTime";

// Setup
const myFormats = ["seconds"];
dayjs.extend(duration);
dayjs.extend(updateLocale);
dayjs.updateLocale("en", {
relativeTime: {
...dayjs.Ls.en.relativeTime,
s: "%d second",
ss: "%d seconds",
m: "%d minute",
h: "%d hour",
d: "%d day",
M: "%d month",
y: "%d year",
yy: "%d years"
}
});
const thresholds = [
{ l: "s", r: 1 },
{ l: "ss", r: myFormats.includes("seconds") ? Infinity : 59, d: "second" },
{ l: "m", r: 1 },
{ l: "mm", r: Infinity, d: "minute" }
];
dayjs.extend(relativeTime, { thresholds });
// "thresholds" contains the right value "Infinity" for the "ss" limiter

// Tests
// Test 1
const sixtySecondsString = "PT60S";
const durationValue = dayjs.duration(sixtySecondsString);
durationValue.humanize(); // Will display "1 minute"

// Test 2
const seventySecondsString = "PT70S";
const durationValueB = dayjs.duration(seventySecondsString);
durationValueB.humanize(); // Will display "1 minute"
```

**Expected behavior**
In my example, I'm expecting "Test A" to display "60 seconds" instead of "1 minute", and "Test B" to display "61 seconds" instead of "1 minute".

My goal is to be able to display any ISO 8601 with strict unit times (i.e. : "PT400H" should display "400 hours" not "17 days")

**Information**
- Day.js Version 1.11.8
- OS: Windows 10
- Browser : None, I'm using Unit Tests for this example, Jest version 25.1.0
- Time zone: +01.00 Paris

Start by running the provided reproduction with the relativeTime, duration, and updateLocale plugins in the project's Jest setup. Inspect how relativeTime thresholds are selected and how duration.humanize converts units. Done means Infinity thresholds preserve the requested seconds and other strict units, with tests covering the reported 60- and 70-second cases.

Written by the indexing model from the issue text.