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GH-43872: [Go][CI] Disable Dependabot for Go (#44102)

### Rationale for this change

As part of moving the go implementation to `arrow-go` we should disable new commits to the main arrow repository.

### What changes are included in this PR?

Remove go config for dependabot.

### Are these changes tested?

No

### Are there any user-facing changes?

No
* GitHub Issue: #43872

Authored-by: Raúl Cumplido <raulcumplido@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>