chore(flamegraph): Lower number of concurrent reads

The new flamegraph endpoint is very likely the suspect of the OOMs we've been
seeing. Upon examining the old flamegraph endpoint, we used to spawn ~25 go
routines per request but at a lower throughput. So having 100 concurrent workers
may be the cause of the OOMs as we try to read too many profiles at once.

cmd/vroom/config.go

@@ -4,7 +4,7 @@ type (
 	ServiceConfig struct {
 		Environment    string `env:"SENTRY_ENVIRONMENT" env-default:"development"`
 		Port           int    `env:"PORT"               env-default:"8085"`
-		WorkerPoolSize int    `env:"WORKER_POOL_SIZE"               env-default:"100"`
+		WorkerPoolSize int    `env:"WORKER_POOL_SIZE"               env-default:"25"`
 
 		SentryDSN string `env:"SENTRY_DSN"`