Remove 'exclude_from_sim' flag from all symbols

KiCad9 introduced a new feature that changes the way symbols with this
flag set are rendered. Now they they rendered are greyed out and crossed
out. This looks quite confusing and is not what was inteded by the
library-team when setting this flag during the v7 cycle.

We want this flag set, so the user will get no error message when trying to
simulate a board that has mounting holes symbols in its schematic.
With some luck, the display in KiCad will be improved/changed in the
future, so we can set this flag again.