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

Followup of prometheus-community#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