refactor: optimize backup return message while cancelled

[mlycore]

Type of change:

• [ ] Bugfix
• [ ] New feature provided
• [ ] Improve performance
• [ ] Backport patches
• [x] Refactor

What this PR does / why we need it:

• Reduce unnecessary log messages while the backup is cancelled.

Pre-submission checklist:

• [ ] Did you explain what problem does this PR solve? Or what new features have been added?
• [ ] Have you added corresponding test cases?
• [ ] Have you modified the corresponding document?

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

No Coverage information
0.0% Duplication

[codecov-commenter]

Codecov Report

Attention: 810 lines in your changes are missing coverage. Please review.

Comparison is base (3604a24) 39.71% compared to head (18931f3) 36.70%. Report is 206 commits behind head on main.

Files	Patch %	Lines
...phere-operator/pkg/controllers/chaos_controller.go	0.00%	276 Missing :warning:
...perator/pkg/controllers/storage_node_controller.go	26.58%	96 Missing and 20 partials :warning:
...operator/pkg/controllers/auto_scaler_controller.go	0.00%	89 Missing :warning:
pitr/cli/internal/cmd/delete.go	61.41%	38 Missing and 11 partials :warning:
pitr/agent/internal/pkg/opengauss.go	2.56%	38 Missing :warning:
pitr/cli/internal/cmd/backup.go	55.26%	32 Missing and 2 partials :warning:
...ator/cmd/shardingsphere-operator/manager/option.go	6.06%	31 Missing :warning:
pitr/cli/internal/pkg/local-storage.go	22.58%	14 Missing and 10 partials :warning:
...ere-operator/pkg/kubernetes/container/container.go	31.25%	22 Missing :warning:
shardingsphere-operator/pkg/kubernetes/helpers.go	46.15%	20 Missing and 1 partial :warning:
... and 12 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #468 +/- ## ========================================== - Coverage 39.71% 36.70% -3.01% ========================================== Files 51 61 +10 Lines 6083 6813 +730 ========================================== + Hits 2416 2501 +85 - Misses 3448 4069 +621 - Partials 219 243 +24 ```

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