You'll find that a lot of spells and effects that used to explicitly say you can willingly fail the saving throw to resist them have had that language removed in the 2024 rules. This is just because there's now a general rule (as Voras pointed out) allowing you to do this for any saving throw, so that language was redundant.
Can an ally willingly fail a saving throw on calm emotions in 5.5e to remove frightened effect?
yes.
PHB 2024 under Saving Throws
"If you don’t want to resist the effect, you can choose to fail the save without rolling."
You'll find that a lot of spells and effects that used to explicitly say you can willingly fail the saving throw to resist them have had that language removed in the 2024 rules. This is just because there's now a general rule (as Voras pointed out) allowing you to do this for any saving throw, so that language was redundant.
pronouns: he/she/they
Thank you.
Thank you so much.