package/fluidsynth: bump to version 2.1.4

package/fluidsynth: bump to version 2.1.4

Changes since v2.1.3:
https://github.com/FluidSynth/fluidsynth/releases/tag/v2.1.4
- fix an uninitialized memory access possibly triggering an FPE trap
- fix several regressions introduced in 2.1.3:
  - fluid_synth_start() failed for certain presets
  - fix a NULL dereference in jack driver
  - fix a stack-based overflow when creating the synth

Signed-off-by: Julien Olivain <juju@cotds.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>