fix(deps): update module github.com/hashicorp/terraform-plugin-mux to v0.21.0

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This PR contains the following updates:

Package	Change	Age	Confidence
github.com/hashicorp/terraform-plugin-mux	v0.20.0 -> v0.21.0

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Release Notes

hashicorp/terraform-plugin-mux (github.com/hashicorp/terraform-plugin-mux)

v0.21.0

Compare Source

NOTES:

• all: This Go module has been updated to Go 1.24 per the Go support policy. It is recommended to review the Go 1.24 release notes before upgrading. Any consumers building on earlier Go versions may experience errors. (#​324)

FEATURES:

• all: Upgraded mux server implementations to support action types. (#​314)
• all: Upgraded mux server implementations to support the new list. (#​313)

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Configuration

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⚠️ 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
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: go.sum

Command failed: go get -t ./...
go: module github.com/hashicorp/[email protected] requires go >= 1.24.0; switching to go1.24.7
go: downloading go1.24.7 (linux/amd64)
go: download go1.24.7: golang.org/[email protected]: verifying module: checksum database disabled by GOSUMDB=off