Fix warning -Wimplicit-fallthrough

[jhasse]

GCC 14 on Fedora

spine-c/src/spine/Debug.c: In function ‘spDebug_printTimeline’:
spine-c/src/spine/Debug.c:210:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
  210 |                         _spDebug_printTimelineBase(&t->super);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
spine-c/src/spine/Debug.c:212:17: note: here
  212 |                 case SP_TIMELINE_INHERIT: {
      |                 ^~~~
spine-c/src/spine/Debug.c:214:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
  214 |                         _spDebug_printTimelineBase(&t->super);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
spine-c/src/spine/Debug.c:216:17: note: here
  216 |                 default: {
      |                 ^~~~~~~
spine-c/src/spine/IkConstraint.c: In function ‘spIkConstraint_apply1’:
spine-c/src/spine/IkConstraint.c:100:36: warning: this statement may fall through [-Wimplicit-fallthrough=]
  100 |                         rotationIK += ATAN2(sc, sa) * RAD_DEG;
      |                                    ^~
spine-c/src/spine/IkConstraint.c:102:17: note: here
  102 |                 default: {
      |                 ^~~~~~~