[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

docs/source/how_to_guides/writing_custom_nodes.md

@@ -142,9 +142,9 @@ databases. [^kedro]
 
 ## References
 
-[^structural-subtyping]: Structural subtyping is similar to ABCs an approach in Python to enforce interfaces, but
-    it can be considered more pythonic since it is closer to duck typing. Hynek Schlawack
-    wrote a comprehensive
+[^structural-subtyping]: Structural subtyping is similar to ABCs an approach in Python to enforce interfaces,
+    but it can be considered more pythonic since it is closer to duck typing. Hynek
+    Schlawack wrote a comprehensive
     [guide on subclassing](https://hynek.me/articles/python-subclassing-redux/) that
     features protocols under "Type 2". Glyph wrote an introduction to protocols called
     [I want a new duck](https://glyph.twistedmatrix.com/2020/07/new-duck.html).