fix: mark tutorial code snippets as ignored in doc tests (#6308)

[swar09]

The code examples in docs/tutorials/date_picker_data.md were failing doc tests because
they reference variables from earlier in the tutorial and require external
blob files that don't exist in the test environment.

Changed code blocks from rust to rust,ignore to properly skip
these tutorial snippets during testing, as they are meant to be integrated
into a larger project rather than run standalone.

Fixes #6308

[CLAassistant]

All committers have signed the CLA.

[robertbastian]

This doesn't fix the issue, does it? An error in date-picker-data.md would still not be caught.

[swar09]

You are right ,
I took the quick route of using ignore because the tutorial code snippets have dependencies on:

1. Variables from earlier code blocks
2. External blob files that don't exist in the test environment

[swar09]

I will update the PR to :

1. Change ,ignore to ,no_run
2. Add the missing imports (use icu::calendar::Gregorian; etc.)
3. Make sure each snippet is enough to compile

This way we catch real errors while acknowledging these are tutorial examples that need external data files to actually run.

Does this approach sound good?