gh-36183: `sage.misc.sageinspect`: fix doctest warnings due to modularisation
We fix the following doctest warnings:
```
sage -t --long --warn-long 30.7 --random-
seed=263240816384135969928803999009622073573
src/sage/misc/sageinspect.py
**********************************************************************
File "src/sage/misc/sageinspect.py", line 1627, in
sage.misc.sageinspect.sage_getargspec
Warning: Variable 'Foo' referenced here was set only in doctest marked
'# needs sage.misc.cython'
sage_getargspec(Foo.join)
**********************************************************************
File "src/sage/misc/sageinspect.py", line 1629, in
sage.misc.sageinspect.sage_getargspec
Warning: Variable 'Bar' referenced here was set only in doctest marked
'# needs sage.misc.cython'
sage_getargspec(Bar.join)
**********************************************************************
File "src/sage/misc/sageinspect.py", line 1631, in
sage.misc.sageinspect.sage_getargspec
Warning: Variable 'Bar' referenced here was set only in doctest marked
'# needs sage.misc.cython'
sage_getargspec(Bar.meet)
[353 tests, 32.04 s]
```
These are (currently) the only warnings I see when running `./sage -t
--long src/sage/misc/`.
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URL: https://github.com/sagemath/sage/pull/36183
Reported by: David Coudert
Reviewer(s): Frédéric Chapoton
