refactor: optimize backup return message while cancelled

[mlycore]

Type of change:

• Bugfix
• New feature provided
• Improve performance
• Backport patches
• 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?

[sonarqubecloud]

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

Additional details and impacted files

@@            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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