Formatted symbol text color not working if used with ["step", ["zoom"], ...] and `get` lookup

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**mapbox-gl-js version**: 2.3.0

**browser**: Chrome 90.0.4430.212 (Official Build) (arm64)

### Steps to Trigger Behavior

1. Code a symbol layer with formatted text
2. Add step zoom expression and with a `get` lookup to the layer
3. Load map on browser
4. Zoom in

For the demo link below:

1. Load the demo page
2. Zoom to at least level 9.5 to see the transition

### Link to Demonstration

https://output.jsbin.com/yecupog/4

https://user-images.githubusercontent.com/2296/120460684-eb656400-c3cb-11eb-9ab7-4adb2d559a1c.mov

### Expected Behavior

`foo 2` label should change to `bar` **and** turn red when zoomed in.

### Actual Behavior

`foo 2` label changes to `bar` **but** doesn't turn red.

### Notes

In the demo linked above, I've added another symbol **without** `['get', 'name']`, the left `foo 1` label. The label color changes to red when zoomed in. I'm not sure if the bug is due to the `get` lookup but this is an unexpected bug nevertheless.

The key difference is between this (no bug):

``` js
9.5, ['format', 'bar', {'text-color': 'red'}],
```

and this (bug):

``` js
9.5, ['format', ['get', 'name'], {'text-color': 'red'}],
```

Start with the linked JSBin reproduction and compare the two symbol-layer expressions: the literal formatted text and the version using `['get', 'name']` inside the zoom `step`. Trace formatted symbol text color evaluation during the zoom transition. Done means the `foo 2` label changes to `bar` and turns red at zoom 9.5 or higher, matching the expected behavior.

Written by the indexing model from the issue text.