fix: don't start auto poll in offline mode

[kp-cat]

Describe the purpose of your pull request

Don't start auto poll in offline mode

Requirement checklist (only if applicable)

• [x] I have covered the applied changes with automated tests.
• [x] I have executed the full automated test set against my changes.
• [x] I have validated my changes against all supported platform versions.
• [x] I have read and accepted the contribution agreement.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (239fd3b) 99.50% compared to head (d2e20c1) 99.50%.

:exclamation: Current head d2e20c1 differs from pull request most recent head 32c3ffe. Consider uploading reports for the commit 32c3ffe to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #20 +/- ## ======================================= Coverage 99.50% 99.50% ======================================= Files 13 13 Lines 1212 1212 ======================================= Hits 1206 1206 Misses 6 6 ``` | [Impacted Files](https://codecov.io/gh/configcat/ruby-sdk/pull/20?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=configcat) | Coverage Δ | | |---|---|---| | [spec/configcat/configcatclient\_spec.rb](https://codecov.io/gh/configcat/ruby-sdk/pull/20?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=configcat#diff-c3BlYy9jb25maWdjYXQvY29uZmlnY2F0Y2xpZW50X3NwZWMucmI=) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=configcat). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=configcat)

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