Fix `fsSelection` field to determine style in JDK applications (eg. Intellij family)

Related: https://youtrack.jetbrains.com/issue/JBR-1776?p=WI-48310

> JDK uses fsSelection field from OS/2 OpenType subtable in font file (https://docs.microsoft.com/en-us/typography/opentype/spec/os2#fsselection) to determine font style. For FiraCodeiScript-Italic.ttf font this field's value (0x40) corresponds to a regular (non-italic) font.