fix(deps): update module golang.org/x/sync to v0.20.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
golang.org/x/sync	v0.17.0 → v0.20.0

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[renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
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The artifact failure details are included below:

File name: .dagger/go.sum

Command failed: go get -t ./...
go: dagger/dagger imports
	dagger/dagger/internal/dagger: package dagger/dagger/internal/dagger is not in std (/opt/containerbase/tools/golang/1.25.5/src/dagger/dagger/internal/dagger)