Colors of feedback buttons are not inverted in dark theme

Cause is the use of rgb(59,63,69) rather than #3b3f45 (which is exactly the same value, just a different 'spelling') in those 2 SVGs, and the code that is doing the replacement is not considering this. Two options:

1. Fix the SVGs.
2. Extend the replacement code.

I went for the latter (it seems more future proof), see https://github.com/musescore/MuseScore/pull/4102

Seems the icon for timewise note entry has a similar issue, it uses rgb(0,0,0) though, here I think it is better to fix the SVG, which I now did and added to my PR

There are some more similar issues: in Preferences/Shortcuts some symbols are getting not inverted, others are.
Not inverted: icons for all the different grace notes and beams, and the parens and brackets for accidentals and noteheads. Those all seem to use #000000
Changing those though affects the palettes too, so is not the way to go I guess.

Fixed in branch master, commit 2029ae55a0

fix #277767: Colors of feedback buttons are not inverted in dark theme

the timewise icon also didn't get inverted in the dark theme, so fix
that in the due course

Fixed in branch master, commit 6315d44cd3

Merge pull request #4102 from Jojo-Schmitz/icons

fix #277767: Colors of feedback buttons are not inverted in dark theme

Automatically closed -- issue fixed for 2 weeks with no activity.