Make PREVENT_STUCK_MODIFIERS the default (#3107)

* Remove chording as it is not documented, not used, and needs work.

* Make Leader Key an optional feature.

* Switch from `PREVENT_STUCK_MODIFIERS` to `STRICT_LAYER_RELEASE`

* Remove `#define PREVENT_STUCK_MODIFIERS` from keymaps.

keyboards/mitosis/config.h

@@ -52,8 +52,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *  These options are also useful to firmware size reduction.
  */
 
-#define PREVENT_STUCK_MODIFIERS
-
 /* disable debug print */
 //#define NO_DEBUG