tools.plot: drop the set_window_title copy once Spatial Math has it (SMTB #263) #789

Spatial Math PR rai-opensource/spatialmath-python#263 adds spatialmath.base.set_window_title(fig, title).

RTB has its own copy in roboticstoolbox/tools/plot.py, which already uses SMTB's when it exists (try: from spatialmath.base import set_window_title). Once the minimum Spatial Math version in pyproject.toml has it:

• require that Spatial Math version
• delete the fallback copy and the try/except
• import set_window_title from spatialmath.base at the call sites (PyPlot, PyPlot2, Vehicle)

Review by 2026-10-28: check whether #263 is merged and released.

Reminder to trigger the same change on MVTB and bdsim (see the linked issues there).