gh-38069: docstrings: Change single dash to double dash after input variables
This is achieved by using variants of the following regex rule:
```
Find: ([ ]*- [^ *()\[\]^]* )-( )
Replace: $1--$2
```
**For the reviewer**: to view the _diff_ succinctly run
`git diff 10.4.beta7 -U0 | grep '^[+-]' | grep -Ev '^(--- a/|\+\+\+
b/)'`
or see the attached file:
[diff.txt](https://github.com/sagemath/sage/files/15447061/diff.txt)
(computed from 307cbf9).
Similar command with colors:
`git diff --color 10.4.beta7 -U0 | grep -Ev 'diff|index|@@|---|\+\+\+'`
URL: https://github.com/sagemath/sage/pull/38069
Reported by: gmou3
Reviewer(s): gmou3, Kwankyu Lee
