Replace another custom implementation of slices.Contains (#1180)

Followup of #1176

Signed-off-by: Cristian Greco <cristian@regolo.cc>

Author: cristiangreco

cmd/postgres_exporter/datasource.go

@@ -18,6 +18,7 @@ import (
 	"net/url"
 	"os"
 	"regexp"
+	"slices"
 	"strings"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -64,11 +65,11 @@ func (e *Exporter) discoverDatabaseDSNs() []string {
 			continue
 		}
 		for _, databaseName := range databaseNames {
-			if contains(e.excludeDatabases, databaseName) {
+			if slices.Contains(e.excludeDatabases, databaseName) {
 				continue
 			}
 
-			if len(e.includeDatabases) != 0 && !contains(e.includeDatabases, databaseName) {
+			if len(e.includeDatabases) != 0 && !slices.Contains(e.includeDatabases, databaseName) {
 				continue
 			}
 

cmd/postgres_exporter/util.go

@@ -24,15 +24,6 @@ import (
 	"github.com/lib/pq"
 )
 
-func contains(a []string, x string) bool {
-	for _, n := range a {
-		if x == n {
-			return true
-		}
-	}
-	return false
-}
-
 // convert a string to the corresponding ColumnUsage
 func stringToColumnUsage(s string) (ColumnUsage, error) {
 	var u ColumnUsage