build(deps): bump google.golang.org/protobuf from 1.31.0 to 1.33.0 in /samples/client/petstore/go

[dependabot]

Bumps google.golang.org/protobuf from 1.31.0 to 1.33.0.

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Summary by cubic

Bumps google.golang.org/protobuf to 1.33.0 in the Go petstore sample and tidies dependencies. Also updates the module to Go 1.23 and cleans go.sum.

• Dependencies

  • Updated google.golang.org/protobuf to 1.33.0 (indirect).
  • Updated golang.org/x/oauth2 to 0.27.0 and github.com/stretchr/testify to 1.10.0.
  • Removed unused deps and added missing indirect test deps; ran go mod tidy.
  • Set go version to 1.23 in go.mod.

• Migration

  • Requires Go 1.23+ to build this sample.

^{Written for commit f7c352b. Summary will update on new commits.}