Remove surrounding whitespace from docstrings

[artofhuman]

Closes #599

I've used ruff with autofix options and rule D210.

ruff check --select D210 . --fix

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (4bce007) 98.31% compared to head (debe1cc) 98.31%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #633 +/- ## ======================================= Coverage 98.31% 98.31% ======================================= Files 13 13 Lines 2557 2557 ======================================= Hits 2514 2514 Misses 43 43 ``` | [Files Changed](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions) | Coverage Δ | | |---|---|---| | [transitions/core.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvY29yZS5weQ==) | `100.00% <ø> (ø)` | | | [transitions/extensions/asyncio.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9hc3luY2lvLnB5) | `97.77% <ø> (ø)` | | | [transitions/extensions/diagrams.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9kaWFncmFtcy5weQ==) | `98.11% <ø> (ø)` | | | [transitions/extensions/diagrams\_base.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9kaWFncmFtc19iYXNlLnB5) | `97.59% <ø> (ø)` | | | [transitions/extensions/diagrams\_graphviz.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9kaWFncmFtc19ncmFwaHZpei5weQ==) | `96.75% <ø> (ø)` | | | [transitions/extensions/diagrams\_pygraphviz.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9kaWFncmFtc19weWdyYXBodml6LnB5) | `99.45% <ø> (ø)` | | | [transitions/extensions/factory.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9mYWN0b3J5LnB5) | `94.73% <ø> (ø)` | | | [transitions/extensions/locking.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9sb2NraW5nLnB5) | `100.00% <ø> (ø)` | | | [transitions/extensions/markup.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9tYXJrdXAucHk=) | `99.34% <ø> (ø)` | | | [transitions/extensions/nesting.py](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions#diff-dHJhbnNpdGlvbnMvZXh0ZW5zaW9ucy9uZXN0aW5nLnB5) | `99.29% <ø> (ø)` | | | ... and [2 more](https://app.codecov.io/gh/pytransitions/transitions/pull/633?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytransitions) | |

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[aleneum]

Hi @artofhuman,

thanks a lot!