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GH-36082: [Release] Do nothing deb bump minor/patch version by post-11-bump-versions.sh on main (#36083)

### Rationale for this change

It's needed on a maintenance branch but not needed on main.

### What changes are included in this PR?

Add the current branch check whether main or not.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* Closes: #36082

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