Removal of long-deprecated APIs

A number of APIs that had been emitting deprecation warnings for several years have been removed:

• IPCompleter.limit_to__all__ configuration option (deprecated since IPython 5.0). Completion on object.<tab> now always uses dir()-based discovery, regardless of __all__.

• IPCompleter.python_matches method (deprecated since IPython 8.27). Use IPCompleter.python_matcher instead.

• OInfo.get() (deprecated since IPython 8.13, added only as a transitional helper when OInfo stopped being a dict in 8.12). Access the dataclass fields directly, e.g. oinfo.found instead of oinfo.get('found').

• The module-level backends and backend2gui attributes of IPython.core.pylabtools (deprecated since IPython 8.24). Matplotlib backends are resolved by Matplotlib itself since 3.9.

• InteractiveShell.run_cell_async and InteractiveShell.should_run_async no longer call transform_cell automatically when transformed_cell is not passed (this fallback had emitted a DeprecationWarning since IPython 7.17); they now raise a TypeError. Run transform_cell yourself and pass the result via the transformed_cell keyword argument (as ipykernel 6.0 and newer already do). InteractiveShell.run_cell is unaffected.