fluidsynth: correctly version guard methods
We bumped the minimum version to 2.1 but the api we used wasn't introduced till version 2.2 of fluidsynth
Followup to !2718 (merged)
We bumped the minimum version to 2.1 but the api we used wasn't introduced till version 2.2 of fluidsynth
Followup to !2718 (merged)