tf_gamerules is the entity that controls respawn wave times. To have a respawn wave time of zero (instant respawn after deathcam plays), create a tf_gamerules entity and a logic_auto entity, then add the output "OnMapSpawn" (or "OnMultiNewRound" for a multi staged map) targeting your gamerules entity with the input "Set[Red/Blue]TeamRespawnWaveTime" with a parameter override of respawn wave time you want, in this case 0. I'd also recommend reading up on the wiki how
respawn waves work to get a better understanding of how TF2 handles respawning. You can also pass a
game_forcespawn entity the input "ForceTeamRespawn" with a parameter override of either 2 or 3 to instantly respawn everybody on either Red or Blue respectively