Remove obsolete dependency on ext-json

[DerManoMann]

Fixes #1973

[github-actions]

Created backport PR for 5.x:

• [Backport #1974 to 5.x] Remove obsolete dependency on ext-json #1975 with remaining conflicts!

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin backport-1974-to-5.x
git worktree add --checkout .worktree/backport-1974-to-5.x backport-1974-to-5.x
cd .worktree/backport-1974-to-5.x
git reset --hard HEAD^
git cherry-pick -x 6ffe4691b54df6f291ad63ff3345c473621c85e6
git push --force-with-lease