Deprecate numeric type python version in PythonVirtualEnvOperator

[starone99]

Deprecate float type python version in PythonVirtualEnvOperator.
If input is 3.10 as float, it is interpreted as python version 3.1.

Also deprecated int type because of consistency.

@BlueHorn07 found the issue.

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[uranusjr]

Personally I’d even remove the int case, being able to pass python_version=3 is not particularly useful and can be rewritten pretty trivially.

We should add a news fragment for this.

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