[FlexibleHeader] Stop running swift tests on Autobot. (#8269)
[FlexibleHeader] Stop running swift tests on Autobot. (#8269)

Closes https://github.com/material-components/material-components-ios/issues/8268

This change only affects Autobot runner. The work to re-enable this flag for Autobot is tracked in #8249.

### Context
Error occurs when testing using Bazel.

```
Test Case '-[components_FlexibleHeader_unit_test_swift_sources.FlexibleHeaderContainerViewControllerTests testTraitCollectionDidChangeBlockCalledWhenTraitCollectionChanges]' started.
Child process terminated with signal 11: Segmentation fault
```
material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios