Update oidc.rst: match example file name to import

[elohmeier]

Just a small typo fix. If users copy the example module reference from below they can avoid the import error if the file is named correctly.

Description of the Change

Checklist

• [x] PR only contains one change (considered splitting up PR)
• [ ] unit-test added
• [x] documentation updated
• [ ] CHANGELOG.md updated (only for user relevant changes)
• [ ] author name in AUTHORS

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (07d2715) 97.56% compared to head (d0e343a) 97.56%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1396 +/- ## ======================================= Coverage 97.56% 97.56% ======================================= Files 32 32 Lines 2132 2132 ======================================= Hits 2080 2080 Misses 52 52 ```

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