Update dependency attrs to v26 (#3044)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

requirements-doc.txt

@@ -1,6 +1,6 @@
 alabaster==1.0.0
 async-generator==1.10
-attrs==25.4.0
+attrs==26.1.0
 Babel==2.18.0
 backcall==0.2.0
 beautifulsoup4==4.14.3