Caps Word activated with `DOUBLE_TAP_SHIFT_TURNS_ON_CAPS_WORD` leaves a a shift modifier stuck even after Caps Word ends

[ohle]

To reproduce:

1. Set CAPS_WORD_ENABLE = yes in rules.mk
2. Set #define DOUBLE_TAP_SHIFT_TURNS_ON_CAPS_WORD in config.h

Double tap the shift key. Caps word comes on and words are capitalized. When hitting space, is_caps_word_on() becomes false, but input is still being capitalized, and there seems to be no way to clear the stuck shift modifier.

Some debug output I added:

splitkb.com:Halcyon Kyria rev4:1: LSFT down: kc=225 caps=0 mods=00 weak=00 oneshot=00
splitkb.com:Halcyon Kyria rev4:1: mods changed: 02 weak=00 oneshot=00 caps=0
splitkb.com:Halcyon Kyria rev4:1: LSFT up: kc=225 caps=0 mods=02 weak=00 oneshot=00
splitkb.com:Halcyon Kyria rev4:1: mods changed: 00 weak=00 oneshot=00 caps=0
splitkb.com:Halcyon Kyria rev4:1: LSFT down: kc=225 caps=0 mods=00 weak=00 oneshot=00
splitkb.com:Halcyon Kyria rev4:1: mods changed: 02 weak=00 oneshot=00 caps=1
splitkb.com:Halcyon Kyria rev4:1: LSFT up: kc=225 caps=1 mods=02 weak=00 oneshot=00

Showing how the second tap of shift enables caps_word (caps=1) and also a shift modifier (mods changed: 02) that does not change back.