Icon redux 01: Remove old insertapplet icons

i#87895 Porting old icon fixes from AOO Bugzilla.
Delete 'insert applet' icons from custom themes.
Checked via git grep core and help source. No instances.

QA - Low risk; visual inspection of icons in general use. Originally icons appeared in insert->object->Applet, circa 2008. See i#86118.

Change-Id: I0221ff8ba3f0ee54aa441feadd73227ee842a632
Signed-off-by: Andrew <dent.ace@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/8370Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>