perf(dependency-health)!: reduce concurrent calls to Ecosystems

I've noticed that in some cases we're seeing HTTP 403s from Ecosystems,
which could be due to the sheer amount of traffic we're sending.

We should significantly reduce this number to avoid the risks of rate
limiting.

This is breaking, as it does introduce a significant increase in
processing time, albeit a very reasonable change to introduce.

Related to #459.

internal/dependencyhealth/generate.go

@@ -19,7 +19,7 @@ import (
 	"github.com/package-url/packageurl-go"
 )
 
-const maxGoroutines = 250
+const maxGoroutines = 25
 
 func Generate(ctx context.Context, logger *slog.Logger, sqlDB *sql.DB, pw progress.Writer, httpClient *http.Client) error {
 	q := db.New(sqlDB)