Replace golang.org/x/exp with stdlib (#2857)

* Replace `golang.org/x/exp` with stdlib

These experimental packages are now available in the Go standard
library since Go 1.21.

	1. golang.org/x/exp/slices -> slices [1]
	2. golang.org/x/exp/maps -> maps [2]

[1]: https://go.dev/doc/go1.21#slices
[2]: https://go.dev/doc/go1.21#maps

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

* Run go mod tidy

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

---------

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
Co-authored-by: Felix Kunde <felix-kunde@gmx.de>

go.mod

@@ -3,6 +3,7 @@ module github.com/zalando/postgres-operator
 go 1.25.0
 
 require (
+	github.com/Masterminds/semver v1.5.0
 	github.com/aws/aws-sdk-go v1.53.8
 	github.com/golang/mock v1.6.0
 	github.com/lib/pq v1.10.9
@@ -12,7 +13,6 @@ require (
 	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.9.0
 	golang.org/x/crypto v0.41.0
-	golang.org/x/exp v0.0.0-20240112132812-db7319d0e0e3
 	gopkg.in/yaml.v2 v2.4.0
 	k8s.io/api v0.30.4
 	k8s.io/apiextensions-apiserver v0.25.9
@@ -21,10 +21,7 @@ require (
 	k8s.io/code-generator v0.25.9
 )
 
-require golang.org/x/tools/go/packages/packagestest v0.1.1-deprecated // indirect
-
 require (
-	github.com/Masterminds/semver v1.5.0
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/emicklei/go-restful/v3 v3.11.0 // indirect
 	github.com/evanphx/json-patch v4.12.0+incompatible // indirect
@@ -62,6 +59,7 @@ require (
 	golang.org/x/text v0.28.0 // indirect
 	golang.org/x/time v0.3.0 // indirect
 	golang.org/x/tools v0.36.0 // indirect
+	golang.org/x/tools/go/packages/packagestest v0.1.1-deprecated // indirect
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/protobuf v1.33.0 // indirect
 	gopkg.in/inf.v0 v0.9.1 // indirect