TST: do we still need tests.extension.arrow.array.ArrowStringArray?

[jbrockmendel]

We have a real one implemented in core.arrays.string_arrow, seems like wasted effort to fix the dummy one up to pass the tests

cc @jorisvandenbossche

[jbrockmendel]

gentle ping @jorisvandenbossche

[jorisvandenbossche]

It's only used for a single test, and that was added in #27674. So we will need to verify that this is tested otherwise as well.

[jbrockmendel]

The relevant test now uses dtype=StringDtype(storage="pyarrow") and the test ArrowStringArray has been removed. Closing.