replicate: fix panic: duplicate metrics collector registration attempted

[philipgough]

• I added CHANGELOG entry for this change.
• Change is not relevant to the end user.

Changes

This change fixes a panic in the thanos bucket tools replicate command

goroutine 1 [running]:
github.com/prometheus/client_golang/prometheus.(*wrappingRegisterer).MustRegister(0xc000677cb0, {0xc00095c090?, 0x1, 0x0?})
/go/pkg/mod/github.com/prometheus/client_golang@v1.15.1/prometheus/wrap.go:104 +0x151
github.com/prometheus/client_golang/prometheus/promauto.Factory.NewGaugeVec({{0x2b24c40?, 0xc000677cb0?}}, {{0x0, 0x0}, {0x0, 0x0}, {0x263a69d, 0x2b}, {0x26603fc, 0x3d}, ...}, ...)
/go/pkg/mod/github.com/prometheus/client_golang@v1.15.1/prometheus/promauto/auto.go:308 +0x1e2
github.com/thanos-io/objstore.WrapWithMetrics({0x2b41110?, 0xc000644960}, {0x2b24c40, 0xc000677cb0}, {0xc000133950, 0x9})
/go/pkg/mod/github.com/thanos-io/objstore@v0.0.0-20230713070940-eb01c83b89a4/objstore.go:434 +0x714
github.com/thanos-io/thanos/pkg/replicate.RunReplicate(0xc00063c948, {0x2b113c0?, 0xc00005f8c0?}, 0xc00063e5f0, {0x400b580?, 0xc000c15bc8?}, {0x25db079, 0xd}, {0x0, 0x0}, ...)
/app/pkg/replicate/replicator.go:144 +0xb92
main.registerBucketReplicate.func1(0x0?, {0x2b113c0, 0xc00005f8c0}, 0x6?, {0x2b24b20, 0x400b580}, 0x70?, 0x0?)
/app/cmd/thanos/tools_bucket.go:749 +0x5b3
main.main()
/app/cmd/thanos/main.go:133 +0x122e

Verification

[squat]

This makes more sense to me :))