fontconfig: Workaround bad hinting in Source Sans Pro Semibold
fontconfig: Workaround bad hinting in Source Sans Pro Semibold

To reproduce run e.g.

```
pango-view --font="Source Sans Pro Semibold 24" --text "acegmnopqrsuvwxyz 1234567890"
```

and witness bad vertical height on some characters, especially e and s.

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