Matplotlib 3.8 contours are now set directly, without iterating through .contours

[mmagnuski]

the tests now print:

borsar/tests/test_viz.py::test_topo
borsar/tests/test_viz.py::test_multi_topo
borsar/tests/test_viz.py::test_multi_topo
borsar/tests/test_viz.py::test_multi_topo
  C:\src\borsar\borsar\viz.py:179: MatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.
    for line in topo.lines.collections:

borsar/tests/test_viz.py::test_topo
borsar/tests/test_viz.py::test_multi_topo
borsar/tests/test_viz.py::test_multi_topo
borsar/tests/test_viz.py::test_multi_topo
  C:\src\borsar\borsar\viz.py:136: MatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.
    lines.collections[rem_ln].remove()

borsar/tests/test_viz.py::test_topo
borsar/tests/test_viz.py::test_multi_topo
borsar/tests/test_viz.py::test_multi_topo
borsar/tests/test_viz.py::test_multi_topo
  C:\src\borsar\borsar\viz.py:138: MatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.
    lines.collections.pop(pop_ln)

borsar/tests/test_viz.py::test_topo
  C:\src\borsar\borsar\viz.py:286: MatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.
    for l in self.lines.collections:

borsar/tests/test_viz.py::test_topo
  C:\src\borsar\borsar\viz.py:298: MatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.
    for l in self.lines.collections:

borsar/tests/test_viz.py::test_multi_topo
borsar/tests/test_viz.py::test_multi_topo
borsar/tests/test_viz.py::test_multi_topo
  C:\src\borsar\borsar\tests\test_viz.py:90: MatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.
    for line in lines.collections:

borsar/tests/test_viz.py::test_topo_simulated_data
  C:\src\borsar\borsar\viz.py:243: MatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.
    [line.set_clip_on(True) for line in topo.lines.collections]

All these should now work without iterating topo.lines.collections, but using topo.lines directly. The easiest "fix" would be to switch to the new syntax and require matplotlib >= 3.8.

[mmagnuski]

see astropy/astropy#15004 for an example fix