stop using deprecated mplot3d parameters

`renderer` argument of mplot3d's `do_3d_projection()` is deprecated in
Matplotlib 3.4. This commit switches from using (also deprecated) `renderer.M`
to `self.axes.M`.

A warning about `renderer` being deprecated is still emitted, but we still
need to keep `renderer=None` statements for reverse compatibility.
23 jobs for master in 9 minutes and 38 seconds (queued for 5 seconds)
Status Name Job ID Coverage
  Build Env
manual build-env:conda #208354
allowed to fail manual
manual build-env:debian #208353
allowed to fail manual
manual build-env:default #208355
allowed to fail manual
manual build-env:ubuntu #208352
allowed to fail manual
 
  Build
passed build:debian #208357

00:02:38

passed build:latest #208360

00:01:56

passed build:no-extras #208359

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passed build:stable #208358

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passed build:ubuntu #208356

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  Test
passed build PDF documentation #208369

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passed build documentation #208368

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passed check for broken links in doc #208370

00:05:55

passed check for dependencies installed #208362

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passed check whitespace style #208361

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passed test:debian #208366

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passed test:latest #208367

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passed test:no-extras #208364

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passed test:stable #208363

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passed test:ubuntu #208365

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  Deploy
manual remove_coverage #208371
allowed to fail manual
manual remove_docs #208373
allowed to fail manual
passed upload dev version docs #208374

00:00:27

passed upload documentation to the test server #208372

00:00:26