fix(upstream): force jsonfeed-util version since it uses a non Python 3.9 syntax, breaking lint and tests (#355)

see: lukasschwab/jsonfeed#15

Author: Guts

requirements/testing.txt

@@ -4,7 +4,7 @@
 # -------
 
 feedparser>=6.0.11,<6.1
-jsonfeed-util>=1.1.2,<2
+jsonfeed-util>=1.1.2,<1.1.4
 mkdocs-material[imaging]>=9.5.47
 pytest-cov>=6,<7
 validator-collection>=1.5,<1.6