deprecated api tri (matplotlib#26909)

* deprecated api tri

* updated deprecated api tri

* updated deprecated api tri

* updated deprecated api tri

* updated deprecated api tri

* pre-commit.ci autofix

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: vigneshvetrivel8

doc/api/next_api_changes/removals/26909-VV.rst

@@ -0,0 +1,4 @@
+``matplotlib.tri`` submodules are removed
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The ``matplotlib.tri.*`` submodules are removed.  All functionality is
+available in ``matplotlib.tri`` directly and should be imported from there.