Update python_api_reference_vDev.md

[tomirendo]

Fixed a typo

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[Strilanc]

I agree this is a typo. Thanks for fixing it! However... you've edited it in a generated file, instead of in the source that generates it. That's why the docs-are-fresh check is failing. If you search for

`X_ERROR(0.1)` followed by a `Z_ERROR(0.2)`. This assu

across the entire code base, you'll find the other places it has to change. Technically it only has to change in the one place under the src/ directory, at which point running dev/regen_docs.sh will do all of the others. Though that script assumes you're on a linux machine; maybe you can't run it easily.

(Potentially also interesting to this particular doc string is that the last version of stim introduced code that attempts to do perfect conversions of PAULI_CHANNEL_1 when possible. The given example is still correct because there's no perfect conversion when one of the three probabilities is set to 0. I think it's fine as is.)

[tomirendo]

Hey Craig, thanks for responding so quickly! I'll rerun the script and push again.
I should learn to do these things by now.
(Also exciting about the decomposition code, I'll comment that as well)

[Strilanc]

Merged into #721