Revert "vochain/indexer: drop x/exp/maps for maps"

This reverts commit e65c7ca.

since we downgraded go back to 1.22

go.mod

@@ -57,6 +57,7 @@ require (
 	go.mongodb.org/mongo-driver v1.12.1
 	go.vocdoni.io/proto v1.15.10-0.20240903073233-86144b1e2165
 	golang.org/x/crypto v0.26.0
+	golang.org/x/exp v0.0.0-20240808152545-0cdaa3abc0fa
 	golang.org/x/net v0.28.0
 	google.golang.org/protobuf v1.34.2
 	lukechampine.com/blake3 v1.3.0
@@ -326,7 +327,6 @@ require (
 	go.uber.org/multierr v1.11.0 // indirect
 	go.uber.org/zap v1.27.0 // indirect
 	go4.org v0.0.0-20230225012048-214862532bf5 // indirect
-	golang.org/x/exp v0.0.0-20240808152545-0cdaa3abc0fa // indirect
 	golang.org/x/mod v0.20.0 // indirect
 	golang.org/x/oauth2 v0.22.0 // indirect
 	golang.org/x/sync v0.8.0 // indirect

vochain/indexer/indexer.go

@@ -9,7 +9,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"maps"
 	"math/big"
 	"os"
 	"path/filepath"
@@ -30,6 +29,7 @@ import (
 	"go.vocdoni.io/proto/build/go/models"
 
 	"github.com/pressly/goose/v3"
+	"golang.org/x/exp/maps"
 
 	// modernc is a pure-Go version, but its errors have less useful info.
 	// We use mattn while developing and testing, and we can swap them later.
@@ -524,7 +524,8 @@ func (idx *Indexer) Commit(height uint32) error {
 	defer idx.blockMu.Unlock()
 
 	// Update existing processes
-	updateProcs := slices.Sorted(maps.Keys(idx.blockUpdateProcs))
+	updateProcs := maps.Keys(idx.blockUpdateProcs)
+	slices.Sort(updateProcs)
 
 	queries := idx.blockTxQueries()
 	ctx := context.TODO()