Unit tests get_all_tables needs to be skipped because Pandas backend does not support list_databases

**Describe the bug**
The test `test_get_all_tables` has to be skipped in Ibis 7.1 because there is no support for list_databases on a pandas client. Please see [here](https://ibis-project.org/concepts/backend-table-hierarchy).

In a future release when we support DuckDB for in memory tables, this unit test can be set up to list databases in duckDB.

**What type of connections are you using for source and target?**
Unit Test

Search the test suite for `test_get_all_tables` and inspect how backend-specific tests are skipped. Confirm the pandas client lacks `list_databases`, then skip this test for that backend and run the relevant unit-test module to verify the suite passes without masking other backends.

Written by the indexing model from the issue text.