`{increase,decrease}FontSize` don't seem to work

# Environment

```none
Windows build number: 19H1 RTM
Windows Terminal version (if applicable): 0.6.3181.0
```

# Steps to reproduce

Press the key bound to `increaseFontSize` (like <kbd>Ctrl+=</kbd> from the default settings).

# Expected behavior

Font size increases.

# Actual behavior

Font size somewhat languishes, wonders what it is doing with its life, goes nowhere.